igc: Enable internal i225 PPS

The i225 device can produce one interrupt on the full second, much
like i210 - from where this patch is inspired.

This patch sets up the full second interruption on the i225 and when
receiving it, it sends a PPS event to PTP (Precision Time Protocol)
kernel subsystem.

The PTP subsystem exposes the PPS events via ioctl and sysfs, and one
can use the `testptp` tool (tools/testing/selftests/ptp) to check that
the events are being generated.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>