e1000e: Add Support for 38.4MHZ frequency

Add support for 38.4MHz frequency is required for PTP
on CannonLake. SYSTIM frequency adjustment attributes for TIMINCA are
get/set dependent on the hardware clock frequency for a different
types of adapters. 38.4MHz frequency supported by CannonLake
and active once time synchronisation mechanism was enabled
Changed abbreviation from Hz to HZ to be compliant checkpatch code style

Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Reviewed-by: Raanan Avargil <raanan.avargil@intel.com>
Reviewed-by: Dima Ruinskiy <dima.ruinskiy@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>