fs: change d_hash for rcu-walk

Change d_hash so it may be called from lock-free RCU lookups. See similar
patch for d_compare for details.

For in-tree filesystems, this is just a mechanical change.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
index e80fea2..50497f6 100644
--- a/fs/gfs2/dentry.c
+++ b/fs/gfs2/dentry.c
@@ -100,7 +100,8 @@
 	return 0;
 }
 
-static int gfs2_dhash(struct dentry *dentry, struct qstr *str)
+static int gfs2_dhash(const struct dentry *dentry, const struct inode *inode,
+		struct qstr *str)
 {
 	str->hash = gfs2_disk_hash(str->name, str->len);
 	return 0;