efi_loader: add file/filesys support

fallback.efi (and probably other things) use UEFI's simple-file-system
protocol and file support to search for OS's to boot.

Signed-off-by: Rob Clark <robdclark@gmail.com>
[agraf: whitespace fixes, unsigned fixes]
Signed-off-by: Alexander Graf <agraf@suse.de>
7 files changed