sfc: mark state UNINIT after unregister

Without this change, modprobe -r sfc hits the BUG_ON() in
efx_pci_remove_main().

Fixes: e7fef9b4 ("sfc: add sysfs entry to control MCDI tracing")
Reported-by: NJarod Wilson <jarod@redhat.com>
Reviewed-by: NJarod Wilson <jarod@redhat.com>
Signed-off-by: NEdward Cree <ecree@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/efx.c

@@ -2920,6 +2920,7 @@ static void efx_pci_remove(struct pci_dev *pci_dev)
 	efx_dissociate(efx);
 	dev_close(efx->net_dev);
 	efx_disable_interrupts(efx);
+	efx->state = STATE_UNINIT;
 	rtnl_unlock();
 
 	if (efx->type->sriov_fini)