drm/panel: ltk050h3146w: only print message when GPIO getting is not EPROBE_DEFER

devm_gpiod_get_optional may return EPROBE_DEFER in case the GPIO
controller isn't yet probed when the panel driver is being probed.

In that case, a spurious and confusing error message about not being
able to get the reset GPIO is printed even though later on the device
actually manages to get probed.

Use dev_err_probe instead so that the message is only printed when it
truly matters.

Cc: Quentin Schulz <[e-mail]>
Signed-off-by: Quentin Schulz <[e-mail]>
Reviewed-by: Christophe JAILLET <[e-mail]>
Signed-off-by: Heiko Stuebner <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/panel/panel-leadtek-ltk050h3146w.c

···
 		return -EINVAL;
 
 	ctx->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
-	if (IS_ERR(ctx->reset_gpio)) {
-		dev_err(dev, "cannot get reset gpio\n");
-		return PTR_ERR(ctx->reset_gpio);
-	}
+	if (IS_ERR(ctx->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(ctx->reset_gpio), "cannot get reset gpio\n");
 
 	ctx->vci = devm_regulator_get(dev, "vci");
 	if (IS_ERR(ctx->vci)) {