drm/i915/lvds: only call intel_lvds_init() on platforms that might have LVDS

With new platforms not having LVDS support, only call intel_lvds_init()
on platforms that might actually have LVDS. Move the comment about eDP
init to the PCH block where it's relevant.

This puts intel_lvds_init() more in line with the rest of the outputs,
and makes it slightly easier for the uninitiated to figure out which
platforms actually have what.

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/20190122082307.4003-2-jani.nikula@intel.com