nfs: declare nfs_callback_tcp_port in header

Sparse warning:
fs/nfs/super.c:2638:16: sparse: symbol 'nfs_callback_tcpport' was not
declared. Should it be static?

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/callback.h b/fs/nfs/callback.h
index c07a8d4..4251c2ae 100644
--- a/fs/nfs/callback.h
+++ b/fs/nfs/callback.h
@@ -208,5 +208,6 @@
 #define NFS41_BC_MAX_CALLBACKS 1
 
 extern unsigned int nfs_callback_set_tcpport;
+extern unsigned short nfs_callback_tcpport;
 
 #endif /* __LINUX_FS_NFS_CALLBACK_H */