staging/lustre: silence gcc build warning

got bellow build warning that is indeed a false alarm.

  CC [M]  drivers/staging/lustre/lustre/llite/llite_nfs.o
  drivers/staging/lustre/lustre/libcfs/nidstrings.c: In function ‘
  libcfs_str2net_internal’:
  drivers/staging/lustre/lustre/libcfs/nidstrings.c:432:17: warning: ‘nf’ may be
  used uninitialized in this function [-Wuninitializ
  ed]

Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/libcfs/nidstrings.c

@@ -414,7 +414,7 @@ libcfs_nid2str(lnet_nid_t nid)
 static struct netstrfns *
 libcfs_str2net_internal(const char *str, __u32 *net)
 {
-	struct netstrfns *nf;
+	struct netstrfns *uninitialized_var(nf);
 	int	       nob;
 	int	       netnum;
 	int	       i;