drm/i915: Nuke intel_get_shared_dpll_id()

Each PLL knows its own ID so intel_get_shared_dpll_id() is
pointless. Get rid of it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220921122343.13061-3-ville.syrjala@linux.intel.com


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