qed: Fix timestamping issue for L2 unicast ptp packets.

commit cedeac9d ("qed: Add support for Timestamping the unicast
PTP packets.") handles the timestamping of L4 ptp packets only.
This patch adds driver changes to detect/timestamp both L2/L4 unicast
PTP packets.

Fixes: cedeac9d ("qed: Add support for Timestamping the unicast PTP packets.")
Signed-off-by: Sudarsana Reddy Kalluru <skalluru@marvell.com>
Signed-off-by: Ariel Elior <aelior@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>