efi/libstub: Avoid protocol wrapper for file I/O routines

efi/libstub: Avoid protocol wrapper for file I/O routines

The EFI file I/O routines built on top of the file I/O firmware
services are incompatible with mixed mode, so there is no need
to obfuscate them by using protocol wrappers whose only purpose
is to hide the mixed mode handling. So let's switch to plain
indirect calls instead.

This also means we can drop the mixed_mode aliases from the various
types involved.

Signed-off-by: Ard Biesheuvel <[email protected]>
Cc: Arvind Sankar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: James Morse <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>