net: mvpp2: ptp: add TAI support

Add support for the TAI block in the mvpp2.2 hardware.

Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>