kernel: Ensure an initramfs is added if configured
If ${DEPLOY_DIR_IMAGE}/${INITRAMFS_IMAGE_NAME}.cpio does not exist,
nor any of the compressed variants, nothing is copied to kernel build's
./usr directory.
The code does not fail, but silently proceeds without a bundled initramfs.
Change to fail and tell the user something is wrong.
Also, if an initramfs is found, contrary to the comments, it does not stop
at the first uncompressed/compressed cpio image found. Instead it keeps
processing all so the last is used. Fix this to behave as per the comments.
[YOCTO #12909]
(Patch by Leon Woestenberg)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
