reset: uniphier-glue: Fix possible null-ptr-deref

It will cause null-ptr-deref when resource_size(res) invoked,
if platform_get_resource() returns NULL.

Fixes: 499fef09 ("reset: uniphier: add USB3 core reset control")
Signed-off-by: Hui Tang <tanghui20@huawei.com>
Reviewed-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Link: https://lore.kernel.org/r/20221114004958.258513-1-tanghui20@huawei.comSigned-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/reset/reset-uniphier-glue.c

@@ -47,7 +47,6 @@ static int uniphier_glue_reset_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct uniphier_glue_reset_priv *priv;
 	struct resource *res;
-	resource_size_t size;
 	int i, ret;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
@@ -60,7 +59,6 @@ static int uniphier_glue_reset_probe(struct platform_device *pdev)
 		return -EINVAL;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	size = resource_size(res);
 	priv->rdata.membase = devm_ioremap_resource(dev, res);
 	if (IS_ERR(priv->rdata.membase))
 		return PTR_ERR(priv->rdata.membase);
@@ -96,7 +94,7 @@ static int uniphier_glue_reset_probe(struct platform_device *pdev)
 
 	spin_lock_init(&priv->rdata.lock);
 	priv->rdata.rcdev.owner = THIS_MODULE;
-	priv->rdata.rcdev.nr_resets = size * BITS_PER_BYTE;
+	priv->rdata.rcdev.nr_resets = resource_size(res) * BITS_PER_BYTE;
 	priv->rdata.rcdev.ops = &reset_simple_ops;
 	priv->rdata.rcdev.of_node = dev->of_node;
 	priv->rdata.active_low = true;