drm/panel: ilitek-ili9881c: Make gpio-reset optional

Depends in how logic is connected to the board the gpio is
not stricly required.
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211016102232.202119-5-michael@amarulasolutions.com

Documentation/devicetree/bindings/display/panel/ilitek,ili9881c.yaml

@@ -27,7 +27,6 @@ required:
   - compatible
   - power-supply
   - reg
-  - reset-gpios
 
 additionalProperties: false
 

drivers/gpu/drm/panel/panel-ilitek-ili9881c.c

@@ -882,7 +882,7 @@ static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi)
 		return dev_err_probe(&dsi->dev, PTR_ERR(ctx->power),
 				     "Couldn't get our power regulator\n");
 
-	ctx->reset = devm_gpiod_get(&dsi->dev, "reset", GPIOD_OUT_LOW);
+	ctx->reset = devm_gpiod_get_optional(&dsi->dev, "reset", GPIOD_OUT_LOW);
 	if (IS_ERR(ctx->reset))
 		return dev_err_probe(&dsi->dev, PTR_ERR(ctx->reset),
 				     "Couldn't get our reset GPIO\n");