drm/i915: Pass intel_encoder to to_lvds_encoder()

Most of our encoder type cast stuff already operates on
intel_encoder rather than drm_encoder. Switch to_lvds_encoder()
over as well.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220912111814.17466-6-ville.syrjala@linux.intel.com


Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>