sfc: Use swap() instead of open coding it

Clean the following coccicheck warning:

./drivers/net/ethernet/sfc/efx_channels.c:870:36-37: WARNING opportunity
for swap().

./drivers/net/ethernet/sfc/efx_channels.c:824:36-37: WARNING opportunity
for swap().
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/efx_channels.c

@@ -819,11 +819,8 @@ int efx_realloc_channels(struct efx_nic *efx, u32 rxq_entries, u32 txq_entries)
 	old_txq_entries = efx->txq_entries;
 	efx->rxq_entries = rxq_entries;
 	efx->txq_entries = txq_entries;
-	for (i = 0; i < efx->n_channels; i++) {
-		channel = efx->channel[i];
-		efx->channel[i] = other_channel[i];
-		other_channel[i] = channel;
-	}
+	for (i = 0; i < efx->n_channels; i++)
+		swap(efx->channel[i], other_channel[i]);
 
 	/* Restart buffer table allocation */
 	efx->next_buffer_table = next_buffer_table;
@@ -865,11 +862,8 @@ int efx_realloc_channels(struct efx_nic *efx, u32 rxq_entries, u32 txq_entries)
 	/* Swap back */
 	efx->rxq_entries = old_rxq_entries;
 	efx->txq_entries = old_txq_entries;
-	for (i = 0; i < efx->n_channels; i++) {
-		channel = efx->channel[i];
-		efx->channel[i] = other_channel[i];
-		other_channel[i] = channel;
-	}
+	for (i = 0; i < efx->n_channels; i++)
+		swap(efx->channel[i], other_channel[i]);
 	goto out;
 }