i40e: add interrupt test

Add a quick ethtool test for interrupts using the SW interrupt.
Also, change the loopback test (for now) to not report failure.

Change-Id: Id8ef154b82475e3163087a8d1df01dfec4d529fc
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index b82f501..8806cab 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -250,6 +250,7 @@
 	u16 globr_count; /* Global reset count */
 	u16 empr_count; /* EMP reset count */
 	u16 pfr_count; /* PF reset count */
+	u16 sw_int_count; /* SW interrupt count */
 
 	struct mutex switch_mutex;
 	u16 lan_vsi;       /* our default LAN VSI */