wic: add support for kernel with initramfs bundled
when INITRAMFS_IMAGE_BUNDLE and INITRAMFS_IMAGE are set, wic should
look for kernel with initramfs image bundled.
Include required variable MACHINE, INITRAMFS_IMAGE_BUNDLE,
INITRAMFS_IMAGE, INITRAMFS_LINK_NAME and KERNEL_IMAGETYPE in WICVARS.
No longer require default value for variable kernel as KERNEL_IMAGETYPE
is not optional variable and included in WICVARS.
image_types_wic to inherit kernel-artifact-names to obtain default
INITRAMFS_LINK_NAME when INITRAMFS_IMAGE_BUNDLE are set.
update wic.Wic2.test_image_env test case to filter optional
variable INITRAMFS_LINK_NAME, INITRAMFS_IMAGE and INITRAMFS_IMAGE_BUNDLE.
Signed-off-by: Chee Yang Lee <chee.yang.lee@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
