e1000e: Fix not generating an error on invalid load parameter

Valid values for InterruptThrottleRate are 10-100000, or one of
0, 1, 3, 4.  '2' is not valid.  This is a legacy from the branching
from the e1000 driver code that e1000e was based from.

Prior to this patch, if the e1000e driver  was loaded with a forced
invalid InterruptThrottleRate of '2', then no throttle rate would be
set and no error message generated.

Now, a message will be generated that an invalid value was used and the
value for InterruptThrottleRate will be set to the default value.

Signed-off-by: Dave Ertman <davidx.m.ertman@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/param.c

@@ -374,6 +374,12 @@ void e1000e_check_options(struct e1000_adapter *adapter)
 				 "%s set to dynamic mode\n", opt.name);
 			adapter->itr = 20000;
 			break;
+		case 2:
+			dev_info(&adapter->pdev->dev,
+				 "%s Invalid mode - setting default\n",
+				 opt.name);
+			adapter->itr_setting = opt.def;
+			/* fall-through */
 		case 3:
 			dev_info(&adapter->pdev->dev,
 				 "%s set to dynamic conservative mode\n",