nfs: Fix nfs_parse_mount_options() kfree() leak

Fix a (small) memory leak in one of the error paths of the NFS mount
options parsing code.

Regression introduced in 2.6.30 by commit a67d18f8 (NFS: load the
rpc/rdma transport module automatically).
Reported-by: NYinghai Lu <yinghai@kernel.org>
Reported-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/nfs/super.c

@@ -1253,6 +1253,7 @@ static int nfs_parse_mount_options(char *raw,
 			default:
 				dfprintk(MOUNT, "NFS:   unrecognized "
 						"transport protocol\n");
+				kfree(string);
 				return 0;
 			}
 			break;