sfc: mark state UNINIT after unregister

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

Fixes: e7fef9b45ae1 ("sfc: add sysfs entry to control MCDI tracing")
Reported-by: Jarod Wilson <jarod@redhat.com>
Reviewed-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Edward Cree <ecree@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 0c42ed9..67bdaf3 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -2920,6 +2920,7 @@
 	efx_dissociate(efx);
 	dev_close(efx->net_dev);
 	efx_disable_interrupts(efx);
+	efx->state = STATE_UNINIT;
 	rtnl_unlock();
 
 	if (efx->type->sriov_fini)