drm/i915/display: Nuke bogus lspcon check

Dropped a irrelevant lspcon check from intel_hdmi_add_properties
function.

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201130204738.2443-10-uma.shankar@intel.com