mtd: rawnand: ams-delta: Handle more GPIO pins as optional

In order to make the driver more useful on platforms other than Amstrad
Delta, allow GPIO descriptor pointers of possibly non-critical NWP and
NCE pins to be initialised as NULL.
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200212003929.6682-10-jmkrzyszt@gmail.com

drivers/mtd/nand/raw/ams-delta.c

@@ -264,14 +264,16 @@ static int ams_delta_init(struct platform_device *pdev)
 	platform_set_drvdata(pdev, priv);
 
 	/* Set chip enabled but write protected */
-	priv->gpiod_nwp = devm_gpiod_get(&pdev->dev, "nwp", GPIOD_OUT_HIGH);
+	priv->gpiod_nwp = devm_gpiod_get_optional(&pdev->dev, "nwp",
+						  GPIOD_OUT_HIGH);
 	if (IS_ERR(priv->gpiod_nwp)) {
 		err = PTR_ERR(priv->gpiod_nwp);
 		dev_err(&pdev->dev, "NWP GPIO request failed (%d)\n", err);
 		return err;
 	}
 
-	priv->gpiod_nce = devm_gpiod_get(&pdev->dev, "nce", GPIOD_OUT_LOW);
+	priv->gpiod_nce = devm_gpiod_get_optional(&pdev->dev, "nce",
+						  GPIOD_OUT_LOW);
 	if (IS_ERR(priv->gpiod_nce)) {
 		err = PTR_ERR(priv->gpiod_nce);
 		dev_err(&pdev->dev, "NCE GPIO request failed (%d)\n", err);