drm/i915/display: Add a WARN for invalid output range and format

Add a WARN to rule out an invalid output range and format
combination. This is to align the lspcon code with
compute_avi_infoframes.

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/20201130204738.2443-6-uma.shankar@intel.com