dts: sparx5: Enable ptp interrupt

Add support for ptp interrupt. This interrupt is used when using 2-step
timestamping. For each timestamp that is added in a queue, an interrupt
is generated.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>