install cd: Use same kernel/initrd for UEFI boot
We currently replace the stock vmlinuz/initrd.img with the ones
built using DIB; however we only replace them for isolinux boot,
leaving UEFI systems booting the stock images from `images/pxeboot/`.
Switch to using the same binaries for both BIOS and UEFI systems.
This applies to both x86_64 and aarch64 EFI systems.
While at it, update EFI grub.cfg to resemble isolinux menu.
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
Change-Id: I305de509a627b36712d29b2f8d51a8c1de09c58e