nfsd: add a MODULE_DESCRIPTION

I got this today from modpost:

    WARNING: modpost: missing MODULE_DESCRIPTION() in fs/nfsd/nfsd.o

Add a module description.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsctl.c

@@ -1627,6 +1627,7 @@ static void __exit exit_nfsd(void)
 }
 
 MODULE_AUTHOR("Olaf Kirch <okir@monad.swb.de>");
+MODULE_DESCRIPTION("In-kernel NFS server");
 MODULE_LICENSE("GPL");
 module_init(init_nfsd)
 module_exit(exit_nfsd)