nfs41: remove uneeded checks in callback processing

All callback operations have arguments to decode and require processing.
The preprocess_nfs4X_op functions catch unsupported or illegal ops so
decode_args and process_op pointers are always non NULL.
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/callback_xdr.c

@@ -630,9 +630,8 @@ static __be32 process_op(uint32_t minorversion, int nop,
 
 	maxlen = xdr_out->end - xdr_out->p;
 	if (maxlen > 0 && maxlen < PAGE_SIZE) {
-		if (likely(op->decode_args != NULL))
 		status = op->decode_args(rqstp, xdr_in, argp);
-		if (likely(status == 0 && op->process_op != NULL))
+		if (likely(status == 0))
 			status = op->process_op(argp, resp);
 	} else
 		status = htonl(NFS4ERR_RESOURCE);