crypto: hisilicon/hpre - use swap() to make code cleaner

Use the macro 'swap()' defined in 'include/linux/minmax.h' to avoid
opencoding it.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Yang Guang <yang.guang5@zte.com.cn>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/hisilicon/hpre/hpre_crypto.c

@@ -1177,13 +1177,10 @@ static void hpre_rsa_exit_tfm(struct crypto_akcipher *tfm)
 static void hpre_key_to_big_end(u8 *data, int len)
 {
 	int i, j;
-	u8 tmp;
 
 	for (i = 0; i < len / 2; i++) {
 		j = len - i - 1;
-		tmp = data[j];
-		data[j] = data[i];
-		data[i] = tmp;
+		swap(data[j], data[i]);
 	}
 }