net: ethernet: ti: netcp: add support of cpts

This patch adds support of the cpts device found in the
gbe and 10gbe ethernet switches on the keystone 2 SoCs
(66AK2E/L/Hx, 66AK2Gx).

Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: WingMan Kwok <w-kwok2@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>