drm/radeon: Add support for the ATIF ACPI method to the radeon driver

By calling the ATIF method in the radeon driver we can make sure
that hotkeys such as the video switch key emit ACPI events when
pressed.

agd5f: fix warning

Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index ab61aaa..a5c1a3e 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -1414,6 +1414,13 @@
 extern void evergreen_disable_interrupt_state(struct radeon_device *rdev);
 extern int evergreen_irq_set(struct radeon_device *rdev);
 
+/* radeon_acpi.c */ 
+#if defined(CONFIG_ACPI) 
+extern int radeon_acpi_init(struct radeon_device *rdev); 
+#else 
+static inline int radeon_acpi_init(struct radeon_device *rdev) { return 0; } 
+#endif 
+
 /* evergreen */
 struct evergreen_mc_save {
 	u32 vga_control[6];