NFSD: Make nfs4_put_copy() static

Clean up: All call sites are in fs/nfsd/nfs4proc.c.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -1285,7 +1285,7 @@ nfsd4_clone(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	return status;
 }
 
-void nfs4_put_copy(struct nfsd4_copy *copy)
+static void nfs4_put_copy(struct nfsd4_copy *copy)
 {
 	if (!refcount_dec_and_test(&copy->refcount))
 		return;

fs/nfsd/state.h

@@ -703,7 +703,6 @@ extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(struct xdr_netobj name
 extern bool nfs4_has_reclaimed_state(struct xdr_netobj name, struct nfsd_net *nn);
 
 void put_nfs4_file(struct nfs4_file *fi);
-extern void nfs4_put_copy(struct nfsd4_copy *copy);
 extern struct nfsd4_copy *
 find_async_copy(struct nfs4_client *clp, stateid_t *staetid);
 extern void nfs4_put_cpntf_state(struct nfsd_net *nn,