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>