drm/panel: ili9341: Respect deferred probe

GPIO controller might not be available when driver is being probed.
There are plenty of reasons why, one of which is deferred probe.

Since GPIOs are optional, return any error code we got to the upper
layer, including deferred probe. With that in mind, use dev_err_probe()
in order to avoid spamming the logs.

Fixes: 5a04227 ("drm/panel: Add ilitek ili9341 panel driver")
Signed-off-by: Andy Shevchenko <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Reviewed-by: Neil Armstrong <[email protected]>
Reviewed-by: Sui Jingfeng <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Neil Armstrong <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: andy-shev

drivers/gpu/drm/panel/panel-ilitek-ili9341.c

@@ -715,11 +715,11 @@ static int ili9341_probe(struct spi_device *spi)
 
 	reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
 	if (IS_ERR(reset))
-		dev_err(dev, "Failed to get gpio 'reset'\n");
+		return dev_err_probe(dev, PTR_ERR(reset), "Failed to get gpio 'reset'\n");
 
 	dc = devm_gpiod_get_optional(dev, "dc", GPIOD_OUT_LOW);
 	if (IS_ERR(dc))
-		dev_err(dev, "Failed to get gpio 'dc'\n");
+		return dev_err_probe(dev, PTR_ERR(dc), "Failed to get gpio 'dc'\n");
 
 	if (!strcmp(id->name, "sf-tc240t-9370-t"))
 		return ili9341_dpi_probe(spi, dc, reset);