sfc: provide dummy definitions of vswitch functions

efx_probe_all() calls efx->type->vswitching_probe during probe. For
SFC4000 (Falcon) NICs this function is not defined, leading to a BUG
with the top of the call stack similar to:
  ? efx_pci_probe_main+0x29a/0x830
  efx_pci_probe+0x7d3/0xe70

vswitching_restore and vswitching_remove also need to be defined.

Fixed in mainline by:
commit 5a6681e2 ("sfc: separate out SFC4000 ("Falcon") support into new sfc-falcon driver")

Fixes: 6d8aaaf6 ("sfc: create VEB vswitch and vport above default firmware setup")
Signed-off-by: Bert Kenward <bkenward@solarflare.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/sfc/falcon.c

@@ -2796,6 +2796,11 @@ const struct efx_nic_type falcon_a1_nic_type = {
 	.timer_period_max =  1 << FRF_AB_TC_TIMER_VAL_WIDTH,
 	.offload_features = NETIF_F_IP_CSUM,
 	.mcdi_max_ver = -1,
+#ifdef CONFIG_SFC_SRIOV
+	.vswitching_probe = efx_port_dummy_op_int,
+	.vswitching_restore = efx_port_dummy_op_int,
+	.vswitching_remove = efx_port_dummy_op_void,
+#endif
 };
 
 const struct efx_nic_type falcon_b0_nic_type = {
@@ -2897,4 +2902,9 @@ const struct efx_nic_type falcon_b0_nic_type = {
 	.offload_features = NETIF_F_IP_CSUM | NETIF_F_RXHASH | NETIF_F_NTUPLE,
 	.mcdi_max_ver = -1,
 	.max_rx_ip_filters = FR_BZ_RX_FILTER_TBL0_ROWS,
+#ifdef CONFIG_SFC_SRIOV
+	.vswitching_probe = efx_port_dummy_op_int,
+	.vswitching_restore = efx_port_dummy_op_int,
+	.vswitching_remove = efx_port_dummy_op_void,
+#endif
 };