NFS: nfs_parsed_mount_options can use unsigned int

fs/nfs/super.c: In function ‘nfs_compare_remount_data’:
fs/nfs/super.c:2042:18: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]
fs/nfs/super.c:2043:18: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]
fs/nfs/super.c:2044:20: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]
fs/nfs/super.c:2046:21: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]
fs/nfs/super.c:2047:21: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]
fs/nfs/super.c:2048:21: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]
fs/nfs/super.c:2049:21: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]
fs/nfs/super.c:2050:18: warning: comparison between signed and
    unsigned integer expressions [-Wsign-compare]

Seen with gcc (GCC) 4.6.3 20120306 (Red Hat 4.6.3-2).

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>