kernel.bbclass: add the runtime dependency on kernel-vmlinux for kernel-image
When a BSP uses vmlinux for boot, the kernel-image package is just
empty. But by default the kernel-vmlinux is not installed. Then the
pkg_postinst_kernel-image() would create a symlink to a non-existent
file. Fix this by adding the runtime dependency on kernel-vmlinux for
kernel-image if the KERNEL_IMAGETYPE is "vmlinux".
Signed-off-by: Kevin Hao <kexin.hao@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
