igb: remove unused temp variable from stats clearing path

There is a temp variable in the stats clearing path that isn't needed since
the results from the stats read can be immediately discared.  Since it
isn't needed we might as well just drop it from the function call.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>