e1000e: Increase PHY PLL clock gate timing

Several packet loss issues were reported for which the root cause for
them was an incorrect configuration of internal HW PHY clock gating
mechanism by SW.
This patch provides the correct mechanism.

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>