drm/edid: Introduce drm_default_rgb_quant_range()

Make the code selecting the RGB quantization range a little less magicy
by wrapping it up in a small helper.

v2: s/adjusted_mode/mode in vc4 to make it actually compile
v3: Add a comment proposed by Eric

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170111141835.25369-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index 0bcfead1..19bd13f 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1330,7 +1330,8 @@ bool intel_hdmi_compute_config(struct intel_encoder *encoder,
 		/* See CEA-861-E - 5.1 Default Encoding Parameters */
 		pipe_config->limited_color_range =
 			pipe_config->has_hdmi_sink &&
-			drm_match_cea_mode(adjusted_mode) > 1;
+			drm_default_rgb_quant_range(adjusted_mode) ==
+			HDMI_QUANTIZATION_RANGE_LIMITED;
 	} else {
 		pipe_config->limited_color_range =
 			intel_hdmi->limited_color_range;