drm/i915/dpll: Use intel_display possible in shared_dpll_mgr hooks

drm/i915/dpll: Use intel_display possible in shared_dpll_mgr hooks

We use intel_display for function hooks of shared_dpll_mgr and
any function that gets called when we use for_each_shared_dpll.
This also contains some opportunistic display->platform.xx changes
all to reductate the use of drm_i915_private.

--v2
-rebase

--v3
-Don't use inline to_i915 [Jani]

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250212074542.3569452-5-suraj.kandpal@intel.com