NFS: Convert v3 into a module

This patch exports symbols and moves over the final structures needed by
the v3 module.  In addition, I also switch over to using IS_ENABLED() to
check if CONFIG_NFS_V3 or CONFIG_NFS_V3_MODULE are set.

The module (nfs3.ko) will be created in the same directory as nfs.ko and
will be automatically loaded the first time you try to mount over NFS v3.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs3super.c b/fs/nfs/nfs3super.c
index 8378090..cc471c7 100644
--- a/fs/nfs/nfs3super.c
+++ b/fs/nfs/nfs3super.c
@@ -14,13 +14,18 @@
 	.sops     = &nfs_sops,
 };
 
-int __init init_nfs_v3(void)
+static int __init init_nfs_v3(void)
 {
 	register_nfs_version(&nfs_v3);
 	return 0;
 }
 
-void exit_nfs_v3(void)
+static void __exit exit_nfs_v3(void)
 {
 	unregister_nfs_version(&nfs_v3);
 }
+
+MODULE_LICENSE("GPL");
+
+module_init(init_nfs_v3);
+module_exit(exit_nfs_v3);