mtd: nand-gpio: don't waste memory for OF failure

We shouldn't try to allocate a resource until we're sure the
of_property_read_u64() call didn't fail. This is especially important if
we use this code for both CONFIG_OF and !CONFIG_OF builds, since
of_property_read_u64() will always return -ENOSYS for !CONFIG_OF.
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/gpio.c

@@ -132,13 +132,17 @@ static int gpio_nand_get_config_of(const struct device *dev,
 
 static struct resource *gpio_nand_get_io_sync_of(struct platform_device *pdev)
 {
-	struct resource *r = devm_kzalloc(&pdev->dev, sizeof(*r), GFP_KERNEL);
+	struct resource *r;
 	u64 addr;
 
-	if (!r || of_property_read_u64(pdev->dev.of_node,
+	if (of_property_read_u64(pdev->dev.of_node,
 				       "gpio-control-nand,io-sync-reg", &addr))
 		return NULL;
 
+	r = devm_kzalloc(&pdev->dev, sizeof(*r), GFP_KERNEL);
+	if (!r)
+		return NULL;
+
 	r->start = addr;
 	r->end = r->start + 0x3;
 	r->flags = IORESOURCE_MEM;