clk: hisilicon: fix potential NULL dereference in hisi_clk_alloc()

platform_get_resource() may fail and return NULL, so we should
better check it's return value to avoid a NULL pointer dereference
a bit later in the code.

This is detected by Coccinelle semantic patch.

@@
expression pdev, res, n, t, e, e1, e2;
@@

res = platform_get_resource(pdev, t, n);
+ if (!res)
+   return -EINVAL;
... when != res == NULL
e = devm_ioremap(e1, res->start, e2);

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Fixes: 322269163a36 ("clk: hisilicon: add hisi_clk_alloc function.")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/hisilicon/clk.c

@@ -49,6 +49,8 @@ struct hisi_clock_data *hisi_clk_alloc(struct platform_device *pdev,
 		return NULL;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return NULL;
 	clk_data->base = devm_ioremap(&pdev->dev,
 				res->start, resource_size(res));
 	if (!clk_data->base)