ptp_ocp: implement DPLL ops

Implement basic DPLL operations in ptp_ocp driver as the
simplest example of using new subsystem.

Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Vadim Fedorenko

drivers/ptp/Kconfig

@@ -188,6 +188,7 @@ config PTP_1588_CLOCK_OCP
 	depends on COMMON_CLK
 	select NET_DEVLINK
 	select CRC16
+	select DPLL
 	help
 	  This driver adds support for an OpenCompute time card.