rxrpc: fix ptr_ret.cocci warnings

net/rxrpc/rxkad.c:1165:1-3: WARNING: PTR_ERR_OR_ZERO can be used

 Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci

CC: David Howells <dhowells@redhat.com>
Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/rxrpc/rxkad.c

@@ -1162,9 +1162,7 @@ static int rxkad_init(void)
 	/* pin the cipher we need so that the crypto layer doesn't invoke
 	 * keventd to go get it */
 	rxkad_ci = crypto_alloc_skcipher("pcbc(fcrypt)", 0, CRYPTO_ALG_ASYNC);
-	if (IS_ERR(rxkad_ci))
-		return PTR_ERR(rxkad_ci);
-	return 0;
+	return PTR_ERR_OR_ZERO(rxkad_ci);
 }
 
 /*