drm/i915/dpcd_bl: Unbreak enable_dpcd_backlight modparam

Looks like I accidentally made it so you couldn't force DPCD backlight
support on, whoops. Fix that.

Signed-off-by: Lyude Paul <[email protected]>
Fixes: 17f5d57 ("drm/i915: Force DPCD backlight mode on X1 Extreme 2nd Gen 4K AMOLED panel")
Cc: Adam Jackson <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: "Ville Syrjälä" <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit d7fb38a)
Signed-off-by: Rodrigo Vivi <[email protected]>

Author: Lyude

drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c

@@ -342,6 +342,7 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
 	 */
 	if (dev_priv->vbt.backlight.type !=
 	    INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE &&
+	    i915_modparams.enable_dpcd_backlight != 1 &&
 	    !drm_dp_has_quirk(&intel_dp->desc, intel_dp->edid_quirks,
 			      DP_QUIRK_FORCE_DPCD_BACKLIGHT)) {
 		DRM_DEV_INFO(dev->dev,