kernel.bbclass: move variables for kernel artifacts names to separate bbclass
* this makes it easier to access these variables from some other bbclass
e.g. sdcard_image-rpi.bbclass in meta-raspberry where we need to know
how some files in deploy are named, but we cannot inherit kernel.bbclass
as it's used in image recipe not kernel recipe
* alternatively we can move these to bitbake.conf like similar image variables are:
meta/conf/bitbake.conf:IMAGE_BASENAME = "${PN}"
meta/conf/bitbake.conf:IMAGE_NAME = "${IMAGE_BASENAME}-${MACHINE}-${DATETIME}"
meta/conf/bitbake.conf:IMAGE_LINK_NAME = "${IMAGE_BASENAME}-${MACHINE}"
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
