sfc: get timer configuration from adapter

On SFN8000 series adapters the MC provides a method to get the timer
quantum and the maximum timer setting. We revert to the old values if the
new call is unavailable.

Signed-off-by: Bert Kenward <bkenward@solarflare.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 3e8c6fb..13b7f52 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -810,6 +810,7 @@
  * @membase: Memory BAR value
  * @interrupt_mode: Interrupt mode
  * @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
  * @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
@@ -941,6 +942,7 @@
 
 	enum efx_int_mode interrupt_mode;
 	unsigned int timer_quantum_ns;
+	unsigned int timer_max_ns;
 	bool irq_rx_adaptive;
 	unsigned int irq_mod_step_us;
 	unsigned int irq_rx_moderation_us;