Save the kernel image name into sysroot so it can be used during image
build if need. This is used by O.S. Systems products and probably
useful to others.
(From OE-Core rev: 19a587cb98a20f0e659483541fc8cec874f6afa9)
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>