mtd: nand: davinci: check required ti,davinci-chipselect property

The property "ti,davinci-chipselect" is required. So we have to check
if it is set.
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Taras Kondratiuk <taras@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/davinci_nand.c

@@ -545,6 +545,9 @@ static struct davinci_nand_pdata
 		if (!of_property_read_u32(pdev->dev.of_node,
 			"ti,davinci-chipselect", &prop))
 			pdev->id = prop;
+		else
+			return ERR_PTR(-EINVAL);
+
 		if (!of_property_read_u32(pdev->dev.of_node,
 			"ti,davinci-mask-ale", &prop))
 			pdata->mask_ale = prop;