net: ethernet: ti: cpts: add support for HW_TS_PUSH events

Hence CPTS IRQ support is in place the W_TS_PUSH events can be added.
PWM capable DmTimers can be used to generete input signals for CPTS on TI
AM335x/AM437x/DRA7 SoCs to be timestamped:
AM335x/AM437x: timer4 - timer7
DRA7/AM57xx: timer13 - timer16

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>