net: macb: Add PTP support to GEM for sama7g5

Add PTP capability to the Gigabit Ethernet MAC.

Signed-off-by: Durai Manickam KR <durai.manickamkr@microchip.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>