drm/radeon: Make radeon_atif_handler static

There are no external users of function radeon_atif_handler so it can
be static.

Signed-off-by: Jean Delvare <[e-mail]>
Cc: Alex Deucher <[e-mail]>
Cc: "Christian König" <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/radeon_acpi.c

···
  * handles it.
  * Returns NOTIFY code
  */
-int radeon_atif_handler(struct radeon_device *rdev,
+static int radeon_atif_handler(struct radeon_device *rdev,
 		struct acpi_bus_event *event)
 {
 	struct radeon_atif *atif = &rdev->atif;

drivers/gpu/drm/radeon/radeon_acpi.h

···
 struct radeon_device;
 struct acpi_bus_event;
 
-int radeon_atif_handler(struct radeon_device *rdev,
-		struct acpi_bus_event *event);
-
 /* AMD hw uses four ACPI control methods:
  * 1. ATIF
  * ARG0: (ACPI_INTEGER) function code