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>

include/acpi/acpi_bus.h

@@ -184,7 +184,7 @@ struct acpi_device_pnp {
 
 #define acpi_device_bid(d)	((d)->pnp.bus_id)
 #define acpi_device_adr(d)	((d)->pnp.bus_address)
-char *acpi_device_hid(struct acpi_device *device);
+const char *acpi_device_hid(struct acpi_device *device);
 #define acpi_device_name(d)	((d)->pnp.device_name)
 #define acpi_device_class(d)	((d)->pnp.device_class)