dpll: add phase_offset_monitor_get/set callback ops

dpll: add phase_offset_monitor_get/set callback ops

Add new callback operations for a dpll device:
- phase_offset_monitor_get(..) - to obtain current state of phase offset
  monitor feature from dpll device,
- phase_offset_monitor_set(..) - to allow feature configuration.

Obtain the feature state value using the get callback and provide it to
the user if the device driver implements callbacks.

Execute the set callback upon user requests.

Reviewed-by: Milena Olech <milena.olech@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250612152835.1703397-3-arkadiusz.kubalewski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>