net: lan966x: Add ptp trap rules

Currently lan966x, doesn't allow to run PTP over interfaces that are
part of the bridge. The reason is when the lan966x was receiving a
PTP frame (regardless if L2/IPv4/IPv6) the HW it would flood this
frame.
Now that it is possible to add VCAP rules to the HW, such to trap these
frames to the CPU, it is possible to run PTP also over interfaces that
are part of the bridge.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>