drm/i915: Mark ns2501 as LVDS without a fixed mode

ns2501 has a builtin scaler so it doesn't need a fixed mode, but
let's still mark it as LVDS instead of TMDS/DVI to make life less
confusing.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200121171100.4370-7-ville.syrjala@linux.intel.com


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