kernel-devicetree.bbclass: Fix and simplify instalation of DTB files

kernel-devicetree.bbclass: Fix and simplify instalation of DTB files

* add 2 new variables:
  KERNEL_DTB_BASE_NAME
  KERNEL_DTB_SYMLINK_NAME
  instead of reusing KERNEL_IMAGE_SYMLINK_NAME and than expecting that
  default value ${MACHINE} was being used in e.g.:
  DTB_SYMLINK_NAME=`echo ${symlink_name} | sed "s/${MACHINE}/${DTB_BASE_NAME}/g"`

* install normal DTB files only once even if there is multiple entries
  in KERNEL_IMAGETYPE_FOR_MAKE and don't prefix them with the type of
  the kernel image, use the KERNEL_IMAGETYPE_FOR_MAKE as a prefix only
  when installing them bundled with kernel or initramfs image.

* deploy the files from ${D}/${KERNEL_IMAGEDEST}/ instead of kernel
  build directory, so that we don't need to call
  DTB_PATH=`get_real_dtb_path_in_kernel "${DTB}"`
  again in do_deploy

* create all links in do_deploy task, because default KERNEL_DTB_BASE_NAME
  like KERNEL_IMAGE_BASE_NAME contains PKGR and PKGR is different in
  do_install and do_deploy, because kernel.bbclass calls
  meta/classes/kernel.bbclass:do_install[prefuncs] += "package_get_auto_pr"
  meta/classes/kernel.bbclass:do_deploy[prefuncs] += "package_get_auto_pr"

* the filenames are a bit different, but with separate variable it
  should be easier for other bbclasses which use these DTB files to
  find them correctly, just use either the cannonical name
  $dtb_base_name.$dtb_ext or $dtb_base_name-${KERNEL_DTB_SYMLINK_NAME}.$dtb_ext
  because PKGR (and other PKG* variables) might be different in your
  task and kernel.do_deploy task.

* fix DTB files being deployed with incorrect filenames when
  KERNEL_IMAGE_SYMLINK_NAME isn't set to ${MACHINE}, e.g. instead of
  the default:
-rw-r--r-- 2 bitbake bitbake 1.4K Nov 20 07:41 deploy/images/raspberrypi3-64/Image-1-4.9.59+git0+e7976b2aff-r0.2-lirc-rpi-20171120043031.dtbo
lrwxrwxrwx 2 bitbake bitbake   64 Nov 20 07:41 deploy/images/raspberrypi3-64/Image-lirc-rpi.dtbo -> Image-1-4.9.59+git0+e7976b2aff-r0.2-lirc-rpi-20171120043031.dtbo
lrwxrwxrwx 2 bitbake bitbake   64 Nov 20 07:41 deploy/images/raspberrypi3-64/lirc-rpi.dtbo -> Image-1-4.9.59+git0+e7976b2aff-r0.2-lirc-rpi-20171120043031.dtbo
  I was getting:
-rw-r--r-- 2 bitbake bitbake 1348 Nov 20 10:28 deploy/images/raspberrypi3-64/Image-linux-raspberrypi-lirc-rpi.dtbo
lrwxrwxrwx 2 bitbake bitbake   37 Nov 20 10:28 deploy/images/raspberrypi3-64/Image-linux-raspberrypi-lirc-rpi-master-20171120102653.dtbo -> Image-linux-raspberrypi-lirc-rpi.dtbo
lrwxrwxrwx 2 bitbake bitbake   37 Nov 20 10:28 deploy/images/raspberrypi3-64/lirc-rpi.dtbo -> Image-linux-raspberrypi-lirc-rpi.dtbo
  and e.g. sdcard_image-rpi.bbclass from meta-raspberrypi:
  https://github.com/agherzan/meta-raspberrypi/blob/37e4e18f4a745ce8dc11f7e40a29da0859ff13c6/classes/sdcard_image-rpi.bbclass
  was failing in:
  mcopy -i ${WORKDIR}/boot.img -s ${DEPLOY_DIR_IMAGE}/${KERNEL_IMAGETYPE}-${DTB_BASE_NAME}.dtb ::${DTB_BASE_NAME}.dtb
  because ${KERNEL_IMAGETYPE}-${DTB_BASE_NAME}.dtb doesn't exist in my
  build, due to
  DTB_SYMLINK_NAME=`echo ${symlink_name} | sed "s/${MACHINE}/${DTB_BASE_NAME}/g"`
  not replacing whole "${KERNEL_IMAGE_SYMLINK_NAME}" (read ${MACHINE})
  with just ${DTB_BASE_NAME}

* with this change applied the deploy dir looks like this:
-rw-r--r-- 2 bitbake bitbake 1.4K Nov 20 15:49 deploy/images/raspberrypi3-64/lirc-rpi-1-4.9.59+git0+e7976b2aff-r0.8-raspberrypi3-64-20171120154716.dtbo
lrwxrwxrwx 2 bitbake bitbake   74 Nov 20 15:49 deploy/images/raspberrypi3-64/lirc-rpi.dtbo -> lirc-rpi-1-4.9.59+git0+e7976b2aff-r0.8-raspberrypi3-64-20171120154716.dtbo
lrwxrwxrwx 2 bitbake bitbake   74 Nov 20 15:49 deploy/images/raspberrypi3-64/lirc-rpi-raspberrypi3-64.dtbo -> lirc-rpi-1-4.9.59+git0+e7976b2aff-r0.8-raspberrypi3-64-20171120154716.dtbo
  and works correctly even with DISTRO using different naming scheme

* the sdcard_image-rpi.bbclass still needs to be modified, I've provided
  updated version here:
  https://github.com/agherzan/meta-raspberrypi/pull/159
* mpc8315e-rdb.conf MACHINE in meta-yocto-bsp also needs small fix:
  https://lists.yoctoproject.org/pipermail/poky/2018-July/011436.html

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>