e1000/e1000: fix compile warning

e1000/e1000e compile report a possible unused variable, fix
that for now.  Shortly after this a small refactor and bug
fix will follow in the same code.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>