spmi-pmic-arb: fix a possible null pointer dereference

If "core" memory resource is not specified, the driver could end up
dereferencing a null pointer.

Fix this by returning -EINVAL when core resource is missing.

Change-Id: Id08f7b2e109b6b2963b19dfe07f07cbfb424202b
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
diff --git a/drivers/spmi/spmi-pmic-arb.c b/drivers/spmi/spmi-pmic-arb.c
index 8105924..a7bf2a1 100644
--- a/drivers/spmi/spmi-pmic-arb.c
+++ b/drivers/spmi/spmi-pmic-arb.c
@@ -1005,6 +1005,12 @@
 	pa->spmic = ctrl;
 
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "core");
+	if (!res) {
+		dev_err(&pdev->dev, "core resource not specified\n");
+		err = -EINVAL;
+		goto err_put_ctrl;
+	}
+
 	pa->core_size = resource_size(res);
 	if (pa->core_size <= 0x800) {
 		dev_err(&pdev->dev, "core_size is smaller than 0x800. Failing Probe\n");