device property: Constify device_get_match_data()

Constify device_get_match_data() as OF and ACPI variants return
constant value.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index bdf47e0..968173e 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -587,7 +587,7 @@ extern int acpi_nvs_for_each_region(int (*func)(__u64, __u64, void *),
 const struct acpi_device_id *acpi_match_device(const struct acpi_device_id *ids,
 					       const struct device *dev);
 
-void *acpi_device_get_match_data(const struct device *dev);
+const void *acpi_device_get_match_data(const struct device *dev);
 extern bool acpi_driver_match_device(struct device *dev,
 				     const struct device_driver *drv);
 int acpi_device_uevent_modalias(struct device *, struct kobj_uevent_env *);
@@ -766,7 +766,7 @@ static inline const struct acpi_device_id *acpi_match_device(
 	return NULL;
 }
 
-static inline void *acpi_device_get_match_data(const struct device *dev)
+static inline const void *acpi_device_get_match_data(const struct device *dev)
 {
 	return NULL;
 }