drm/i915/dsi: unify connector/encoder type and name usage

Stop using struct drm_* local variables and parameters where
possible. Drop the intel_ prefix from struct intel_encoder and
intel_connector local variable and parameter names. Drop useless
intermediate variables.
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/7aa8fbaa2ecbe2400255964d49aba40cfe0479c5.1713520813.git.jani.nikula@intel.comSigned-off-by: Jani Nikula <jani.nikula@intel.com>