switch open-coded instances of d_make_root() to new helper

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index 00de2c9..256f852 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -655,9 +655,8 @@
 		dout("open_root_inode success\n");
 		if (ceph_ino(inode) == CEPH_INO_ROOT &&
 		    fsc->sb->s_root == NULL) {
-			root = d_alloc_root(inode);
+			root = d_make_root(inode);
 			if (!root) {
-				iput(inode);
 				root = ERR_PTR(-ENOMEM);
 				goto out;
 			}