drm/i915: remove the extra modeset init layer

Streamline the modeset init by removing the extra init layer.

No functional changes, which means the cleanup path looks hideous.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/62c32c35683b843ecdc2eca2bd2d3e62cb705e96.1599056955.git.jani.nikula@intel.com