Xen has its own version of the image header, to account for the
additional PE/COFF header fields. Since we are adding references to
those in the shared EFI loader code, update the common definitions
and drop the Xen specific one which no longer has a purpose.
Since in both cases, the call to grub_arch_efi_linux_check_image() is
preceded by a load of the image header, let's move the load into that
function, and rename it to grub_arch_efi_linux_load_image_header().
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>