sfc: don't free_irq()s if they were never requested

If efx_nic_init_interrupt fails, or was never run (e.g. due to an earlier
 failure in ef100_net_open), freeing irqs in efx_nic_fini_interrupt is not
 needed and will cause error messages and stack traces.
So instead, only do this if efx_nic_init_interrupt successfully completed,
 as indicated by the new efx->irqs_hooked flag.

Fixes: 965b549f3c20 ("sfc_ef100: implement ndo_open/close and EVQ probing")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index dcb741d..062462a 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -846,6 +846,7 @@ struct efx_async_filter_insertion {
  * @timer_quantum_ns: Interrupt timer quantum, in nanoseconds
  * @timer_max_ns: Interrupt timer maximum value, in nanoseconds
  * @irq_rx_adaptive: Adaptive IRQ moderation enabled for RX event queues
+ * @irqs_hooked: Channel interrupts are hooked
  * @irq_rx_mod_step_us: Step size for IRQ moderation for RX event queues
  * @irq_rx_moderation_us: IRQ moderation time for RX event queues
  * @msg_enable: Log message enable flags
@@ -1004,6 +1005,7 @@ struct efx_nic {
 	unsigned int timer_quantum_ns;
 	unsigned int timer_max_ns;
 	bool irq_rx_adaptive;
+	bool irqs_hooked;
 	unsigned int irq_mod_step_us;
 	unsigned int irq_rx_moderation_us;
 	u32 msg_enable;