drm/i915/dpll: convert intel_dpll.[ch] to struct intel_display

Going forward, struct intel_display is the main display device data
pointer. Convert as much as possible of intel_dpll.[ch] to struct
intel_display.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/16fe331ba51c269d6f9871d7b0a3b8df3c7b5342.1742906146.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>