[PATCH] sparse: fix ugly include/linux/efi.h typedef

efi.h declares a function type, and then uses that as an argument to
another function, and expects the compiler to magically demote the
function to a function pointer.

Even a gcc person (rth) was surprised that this was legal, and it
doesn't match any other use of a function pointer in the kernel, and
sparse doesn't like the implicit type-conversion.

So make the type sane in the first place, instead of depending on
a very weird corner case of the C language.

include/linux/efi.h

@@ -108,7 +108,7 @@ typedef struct {
 #endif
 } efi_memory_desc_t;
 
-typedef int efi_freemem_callback_t (unsigned long start, unsigned long end, void *arg);
+typedef int (*efi_freemem_callback_t) (unsigned long start, unsigned long end, void *arg);
 
 /*
  * Types and defines for Time Services