Nothing defined in the header is used by drivers/firmware/efi/sysfb_efi.c
but also, including it can lead to build errors when built on arches that
don't have an asm/efi.h header file.

This can happen for example if a driver that is built when COMPILE_TEST is
enabled selects the SYSFB symbol, e.g. on powerpc with allyesconfig:

drivers/firmware/efi/sysfb_efi.c:29:10: fatal error: asm/efi.h: No such file or directory
   29 | #include <asm/efi.h>
      |          ^~~~~~~~~~~
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>