vfs: export full_name_hash() function to modules

Commit 5707c87f "vfs: uninline full_name_hash()" broke the modular
build, because it needs exporting now that it isn't inlined any more.

Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namei.c

@@ -1381,6 +1381,7 @@ unsigned int full_name_hash(const unsigned char *name, unsigned int len)
 		hash = partial_name_hash(*name++, hash);
 	return end_name_hash(hash);
 }
+EXPORT_SYMBOL(full_name_hash);
 
 /*
  * We know there's a real path component here of at least