video/efi_gop: Remove unnecessary return value of grub_video_gop_fill_mode_info()

video/efi_gop: Remove unnecessary return value of grub_video_gop_fill_mode_info()

The return value of grub_video_gop_fill_mode_info() is never able to be
anything other than GRUB_ERR_NONE. So, rather than continue to return
a value and checking it each time, it is more correct to redefine the
function to not return anything and remove checks of its return value
altogether.

Fixes: CID 96701
Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>