video: meson: hdmi-supply regulator should be optional

Some boards don't have such a regulator, and don't need one to enable
HDMI display. Make it optional, fixing hdmi display for those boards.

Also surround the regulator code with a config check on DM_REGULATOR.

Reported-by: Mohammad Rasim <mohammad.rasim96@gmail.com>
Signed-off-by: Maxime Jourdan <mjourdan@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Mohammad Rasim <mohammad.rasim96@gmail.com>
diff --git a/drivers/video/meson/meson_dw_hdmi.c b/drivers/video/meson/meson_dw_hdmi.c
index 7a1c060..483c93f 100644
--- a/drivers/video/meson/meson_dw_hdmi.c
+++ b/drivers/video/meson/meson_dw_hdmi.c
@@ -361,13 +361,19 @@
 	priv->hdmi.i2c_clk_high = 0x67;
 	priv->hdmi.i2c_clk_low = 0x78;
 
+#if CONFIG_IS_ENABLED(DM_REGULATOR)
 	ret = device_get_supply_regulator(dev, "hdmi-supply", &supply);
-	if (ret)
+	if (ret && ret != -ENOENT) {
+		pr_err("Failed to get HDMI regulator\n");
 		return ret;
+	}
 
-	ret = regulator_set_enable(supply, true);
-	if (ret)
-		return ret;
+	if (!ret) {
+		ret = regulator_set_enable(supply, true);
+		if (ret)
+			return ret;
+	}
+#endif
 
 	ret = reset_get_bulk(dev, &resets);
 	if (ret)