slimbus: qcom: fix potential NULL dereference in qcom_slim_prg_slew()

platform_get_resource_byname() may fail and in this case a NULL
dereference will occur.

Fix it to use devm_platform_ioremap_resource_byname() instead of calling
platform_get_resource_byname() and devm_ioremap().

This is detected by Coccinelle semantic patch.

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

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

Fixes: ad7fcbc308b0 ("slimbus: qcom: Add Qualcomm Slimbus controller driver")
Signed-off-by: Zhang Changzhong <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/slimbus/qcom-ctrl.c

···
 static void qcom_slim_prg_slew(struct platform_device *pdev,
 				struct qcom_slim_ctrl *ctrl)
 {
-	struct resource	*slew_mem;
-
 	if (!ctrl->slew_reg) {
 		/* SLEW RATE register for this SLIMbus */
-		slew_mem = platform_get_resource_byname(pdev, IORESOURCE_MEM,
-				"slew");
-		ctrl->slew_reg = devm_ioremap(&pdev->dev, slew_mem->start,
-				resource_size(slew_mem));
-		if (!ctrl->slew_reg)
+		ctrl->slew_reg = devm_platform_ioremap_resource_byname(pdev, "slew");
+		if (IS_ERR(ctrl->slew_reg))
 			return;
 	}