SUNRPC: Push svcxdr_init_decode() into svc_process_common()

Now that all vs_dispatch functions invoke svcxdr_init_decode(), it
is common code and can be pushed down into the generic RPC server.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/lockd/svc.c

@@ -695,7 +695,6 @@ static int nlmsvc_dispatch(struct svc_rqst *rqstp, __be32 *statp)
 {
 	const struct svc_procedure *procp = rqstp->rq_procinfo;
 
-	svcxdr_init_decode(rqstp);
 	if (!procp->pc_decode(rqstp, &rqstp->rq_arg_stream))
 		goto out_decode_err;
 

fs/nfs/callback_xdr.c

@@ -984,7 +984,6 @@ nfs_callback_dispatch(struct svc_rqst *rqstp, __be32 *statp)
 {
 	const struct svc_procedure *procp = rqstp->rq_procinfo;
 
-	svcxdr_init_decode(rqstp);
 	svcxdr_init_encode(rqstp);
 
 	*statp = procp->pc_func(rqstp);

fs/nfsd/nfssvc.c

@@ -1040,7 +1040,6 @@ int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp)
 	 */
 	rqstp->rq_cachetype = proc->pc_cachetype;
 
-	svcxdr_init_decode(rqstp);
 	if (!proc->pc_decode(rqstp, &rqstp->rq_arg_stream))
 		goto out_decode_err;
 

net/sunrpc/svc.c

@@ -1302,6 +1302,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 	if (progp == NULL)
 		goto err_bad_prog;
 
+	svcxdr_init_decode(rqstp);
 	rpc_stat = progp->pg_init_request(rqstp, progp, &process);
 	switch (rpc_stat) {
 	case rpc_success: