net: ethernet: ti: cpts: move dt props parsing to cpts driver

Move DT properties parsing into CPTS driver to simplify CPSW
code and CPTS driver porting on other SoC in the future
(like Keystone 2) - with this change it will not be required
to add the same DT parsing code in Keystone 2 NETCP driver.

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