drm/i915/dpcd_bl: uncheck PWM_PIN_CAP when detect eDP backlight capabilities

BOE panel with ID 2270 claims both PWM_PIN_CAP and AUX_SET_CAP backlight
control bits, but default chip backlight failed to control brightness.

Check AUX_SET_CAP and proceed to check quirks or VBT backlight type.
DPCD can control the brightness of this pannel.
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201009085750.88490-1-aaron.ma@canonical.com

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

@@ -343,8 +343,7 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector)
 	 * the panel can support backlight control over the aux channel
 	 */
 	if (intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP &&
-	    (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP) &&
-	    !(intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)) {
+	    (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
 		drm_dbg_kms(&i915->drm, "AUX Backlight Control Supported!\n");
 		return true;
 	}