sfc/siena: fix TX channel offset when using legacy interrupts

As in previous commit for sfc, fix TX channels offset when
efx_siena_separate_tx_channels is false (the default)

Fixes: 25bde571 ("sfc/siena: fix wrong tx channel offset with efx_separate_tx_channels")
Reported-by: Tianhao Zhao <tizhao@redhat.com>
Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Link: https://lore.kernel.org/r/20220915141653.15504-1-ihuguet@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/sfc/siena/efx_channels.c

@@ -320,7 +320,7 @@ int efx_siena_probe_interrupts(struct efx_nic *efx)
 		efx->n_channels = 1 + (efx_siena_separate_tx_channels ? 1 : 0);
 		efx->n_rx_channels = 1;
 		efx->n_tx_channels = 1;
-		efx->tx_channel_offset = 1;
+		efx->tx_channel_offset = efx_siena_separate_tx_channels ? 1 : 0;
 		efx->n_xdp_channels = 0;
 		efx->xdp_channel_offset = efx->n_channels;
 		efx->legacy_irq = efx->pci_dev->irq;