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>
diff --git a/fs/namei.c b/fs/namei.c
index 71807dc..e2ba628 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1381,6 +1381,7 @@
 		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