drm/i915/backlight: Honor VESA eDP backlight luminance control capability

The VESA AUX backlight fails to be enable luminance based backlight
mainpulation becaused luminance_set is false by default.
Fix it by using luminance support control capabitliy.

Fixes: e13af51 ("drm/i915/backlight: Use drm helper to initialize edp backlight")
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://lore.kernel.org/r/20250823121647.275834-1-aaron.ma@canonical.com

Author: pyma1

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

@@ -530,7 +530,7 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
 				     luminance_range->max_luminance,
 				     panel->vbt.backlight.pwm_freq_hz,
 				     intel_dp->edp_dpcd, &current_level, &current_mode,
-				     false);
+				     panel->backlight.edp.vesa.luminance_control_support);
 	if (ret < 0)
 		return ret;