AFS: Fix compilation warning

Fix the following warning:

  fs/afs/dir.c: In function 'afs_d_revalidate':
  fs/afs/dir.c:567: warning: 'fid.vnode' may be used uninitialized in this function
  fs/afs/dir.c:567: warning: 'fid.unique' may be used uninitialized in this function

by marking the 'fid' variable as an uninitialized_var.  The problem is
that gcc doesn't always manage to work out that fid is always set on the
path through the function that uses it.

Cc: linux-afs@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 9bd7577..88067f3 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -564,7 +564,7 @@
 static int afs_d_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
 	struct afs_vnode *vnode, *dir;
-	struct afs_fid fid;
+	struct afs_fid uninitialized_var(fid);
 	struct dentry *parent;
 	struct key *key;
 	void *dir_version;