sfc: Move TX queue core queue mapping into tx.c

efx_hard_start_xmit() needs to implement a mapping which is the
inverse of tx_queue::core_txq.  Move the initialisation of
tx_queue::core_txq next to efx_hard_start_xmit() to make the
connection more obvious.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 002bac7..c559bc3 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -1910,10 +1910,8 @@
 
 	efx_for_each_channel(channel, efx) {
 		struct efx_tx_queue *tx_queue;
-		efx_for_each_channel_tx_queue(tx_queue, channel) {
-			tx_queue->core_txq = netdev_get_tx_queue(
-				efx->net_dev, tx_queue->queue / EFX_TXQ_TYPES);
-		}
+		efx_for_each_channel_tx_queue(tx_queue, channel)
+			efx_init_tx_queue_core_txq(tx_queue);
 	}
 
 	/* Always start with carrier off; PHY events will detect the link */