Call efx_set_channels() before efx->type->dimension_resources()

When using the "separate_tx_channels=1" module parameter, the TX queues are
initially numbered starting from the first TX-only channel number (after all the
RX-only channels).  efx_set_channels() renumbers the queues so that they are
indexed from zero.

On EF10, the TX queues need to be relabelled in this way before calling the
dimension_resources NIC type operation, otherwise the TX queue PIO buffers can be
linked to the wrong VIs when using "separate_tx_channels=1".

Added comments to explain UC/WC mappings for PIO buffers

Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 52589f6..57b971e 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -1599,6 +1599,8 @@
 	if (rc)
 		goto fail1;
 
+	efx_set_channels(efx);
+
 	rc = efx->type->dimension_resources(efx);
 	if (rc)
 		goto fail2;
@@ -1609,7 +1611,6 @@
 		efx->rx_indir_table[i] =
 			ethtool_rxfh_indir_default(i, efx->rss_spread);
 
-	efx_set_channels(efx);
 	netif_set_real_num_tx_queues(efx->net_dev, efx->n_tx_channels);
 	netif_set_real_num_rx_queues(efx->net_dev, efx->n_rx_channels);