crypto: essiv - remove redundant null pointer check before kfree

kfree has taken null pointer check into account. so it is safe to
remove the unnecessary check.
Signed-off-by: NChen Wandun <chenwandun@huawei.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

crypto/essiv.c

@@ -188,8 +188,7 @@ static void essiv_aead_done(struct crypto_async_request *areq, int err)
 	struct aead_request *req = areq->data;
 	struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
 
-	if (rctx->assoc)
-		kfree(rctx->assoc);
+	kfree(rctx->assoc);
 	aead_request_complete(req, err);
 }