util/grub-mkrescue: Add support for FAT and NTFS on EFI boot

util/grub-mkrescue: Add support for FAT and NTFS on EFI boot

In order to add file system transposition support for UEFI, i.e. the ability
to copy the content of an grub-mkrescue ISO 9660 image onto user-formatted
media, and have that boot on UEFI systems, the first thing we need to do is
add support for the file systems that are natively handled by UEFI. This
mandatorily includes FAT, but we also include NTFS as the latter is also
commonly supported on modern x64 platforms.

Signed-off-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>