drm/panel: himax-hx8394: switch to devm_gpiod_get_optional() for reset_gpio

Switch the driver to use devm_gpiod_get_optional() on reset_gpio to avoid
driver probe issues when reset line is not specified.
Signed-off-by: Manikandan Muralidharan <manikandan.m@microchip.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240701085837.50855-3-manikandan.m@microchip.comSigned-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240701085837.50855-3-manikandan.m@microchip.com

drivers/gpu/drm/panel/panel-himax-hx8394.c

@@ -486,7 +486,7 @@ static int hx8394_probe(struct mipi_dsi_device *dsi)
 	if (!ctx)
 		return -ENOMEM;
 
-	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	ctx->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
 	if (IS_ERR(ctx->reset_gpio))
 		return dev_err_probe(dev, PTR_ERR(ctx->reset_gpio),
 				     "Failed to get reset gpio\n");