drm/panel: atna33xc20: Fix unbalanced regulator in the case HPD doesn't assert

When the atna33xc20 driver was first written the resume code never
returned an error. If there was a problem waiting for HPD it just
printed a warning and moved on. This changed in response to review
feedback [1] on a future patch but I accidentally didn't account for
rolling back the regulator enable in the error cases. Do so now.

[1] https://lore.kernel.org/all/5f3cf3a6-1cc2-63e4-f76b-4ee686764705@linaro.org/

Fixes: 3b5765df ("drm/panel: atna33xc20: Take advantage of wait_hpd_asserted() in struct drm_dp_aux")
Acked-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240313-homestarpanel-regulator-v1-1-b8e3a336da12@chromium.org

drivers/gpu/drm/panel/panel-samsung-atna33xc20.c

@@ -109,19 +109,17 @@ static int atana33xc20_resume(struct device *dev)
 		if (hpd_asserted < 0)
 			ret = hpd_asserted;
 
-		if (ret)
+		if (ret) {
 			dev_warn(dev, "Error waiting for HPD GPIO: %d\n", ret);
-
-		return ret;
-	}
-
-	if (p->aux->wait_hpd_asserted) {
+			goto error;
+		}
+	} else if (p->aux->wait_hpd_asserted) {
 		ret = p->aux->wait_hpd_asserted(p->aux, HPD_MAX_US);
 
-		if (ret)
+		if (ret) {
 			dev_warn(dev, "Controller error waiting for HPD: %d\n", ret);
-
-		return ret;
+			goto error;
+		}
 	}
 
 	/*
@@ -133,6 +131,12 @@ static int atana33xc20_resume(struct device *dev)
 	 * right times.
 	 */
 	return 0;
+
+error:
+	drm_dp_dpcd_set_powered(p->aux, false);
+	regulator_disable(p->supply);
+
+	return ret;
 }
 
 static int atana33xc20_disable(struct drm_panel *panel)