e1000e: Increase ULP timer

Due to system level changes introduced in Skylake, ULP exit takes
significantly longer to occur.  Therefore, driver must wait longer for.

Signed-off-by: Raanan Avargil <raanan.avargil@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>