drm/amd/display: Don't allow OLED to go down to fully off

[Why]
OLED panels can be fully off, but this behavior is unexpected.

[How]
Ensure that minimum luminance is at least 1.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4338
Reviewed-by: Alex Hung <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Ray Wu <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
(cherry picked from commit 51496c7)

Author: superm1

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -3610,13 +3610,15 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
 
 	luminance_range = &conn_base->display_info.luminance_range;
 
-	if (luminance_range->max_luminance) {
-		caps->aux_min_input_signal = luminance_range->min_luminance;
+	if (luminance_range->max_luminance)
 		caps->aux_max_input_signal = luminance_range->max_luminance;
-	} else {
-		caps->aux_min_input_signal = 0;
+	else
 		caps->aux_max_input_signal = 512;
-	}
+
+	if (luminance_range->min_luminance)
+		caps->aux_min_input_signal = luminance_range->min_luminance;
+	else
+		caps->aux_min_input_signal = 1;
 
 	min_input_signal_override = drm_get_panel_min_brightness_quirk(aconnector->drm_edid);
 	if (min_input_signal_override >= 0)