dpll: spec: add support for pin-dpll signal phase offset/adjust

Add attributes for providing the user with:
- measurement of signals phase offset between pin and dpll
- ability to adjust the phase of pin signal

Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>