efi/libstub: Make the LoadFile EFI protocol accessible

Add the protocol definitions, GUIDs and mixed mode glue so that
the EFI loadfile protocol can be used from the stub. This will
be used in a future patch to load the initrd.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

arch/x86/include/asm/efi.h

@@ -291,6 +291,10 @@ static inline void *efi64_zero_upper(void *p)
 	((protocol), efi64_zero_upper(seg), efi64_zero_upper(bus),	\
 	 efi64_zero_upper(dev), efi64_zero_upper(func))
 
+/* LoadFile */
+#define __efi64_argmap_load_file(protocol, path, policy, bufsize, buf)	\
+	((protocol), (path), (policy), efi64_zero_upper(bufsize), (buf))
+
 /*
  * The macros below handle the plumbing for the argument mapping. To add a
  * mapping for a specific EFI method, simply define a macro