drm/i915: Nuke {pipe,plane}_to_crtc_mapping[]

These plane/pipe->crtc mapping arrays are rather pointless.
Get rid of them and just iterate the lists instead.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211203112029.1057-1-ville.syrjala@linux.intel.com


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