clk: imx: fix potential NULL dereference in imx8qxp_lpcg_clk_probe()

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);

Fixes: 1e3121bfe5 ("clk: imx: add imx8qxp lpcg driver")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/imx/clk-imx8qxp-lpcg.c

@@ -169,6 +169,8 @@ static int imx8qxp_lpcg_clk_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
 	base = devm_ioremap(dev, res->start, resource_size(res));
 	if (!base)
 		return -ENOMEM;