perf/arm-cmn: Fix incorrect error check for devm_ioremap()

Check devm_ioremap() return value for NULL instead of ERR_PTR and return
-ENOMEM on failure. devm_ioremap() never returns ERR_PTR, using IS_ERR()
skips the error path and may cause a NULL pointer dereference.

Fixes: 5394396 ("perf/arm-cmn: Stop claiming entire iomem region")
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Signed-off-by: Will Deacon <will@kernel.org>

Author: Chen Ni

drivers/perf/arm-cmn.c

@@ -2573,8 +2573,8 @@ static int arm_cmn_probe(struct platform_device *pdev)
 
 	/* Map the whole region now, claim the DTCs once we've found them */
 	cmn->base = devm_ioremap(cmn->dev, cfg->start, resource_size(cfg));
-	if (IS_ERR(cmn->base))
-		return PTR_ERR(cmn->base);
+	if (!cmn->base)
+		return -ENOMEM;
 
 	rootnode = arm_cmn_get_root(cmn, cfg);
 	if (rootnode < 0)