ACPI/PNP: A HID value of an object never changes -> make it const

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
index 1575a9b..71ef9cd 100644
--- a/drivers/acpi/button.c
+++ b/drivers/acpi/button.c
@@ -338,7 +338,8 @@
 {
 	struct acpi_button *button;
 	struct input_dev *input;
-	char *hid, *name, *class;
+	const char *hid = acpi_device_hid(device);
+	char *name, *class;
 	int error;
 
 	button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
@@ -353,7 +354,6 @@
 		goto err_free_button;
 	}
 
-	hid = acpi_device_hid(device);
 	name = acpi_device_name(device);
 	class = acpi_device_class(device);