net: ethernet: ti: cpts: optimize packet to event matching

Now the CPTS driver performs packet (skb) parsing every time when it needs
to match packet to CPTS event (including ptp_classify_raw() calls).

This patch optimizes matching process by parsing packet only once upon
arrival and stores PTP specific data in skb->cb using the same fromat as in
CPTS HW event. As result, all future matching reduces to comparing two u32
values.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>