drm/radeon: add get_xclk() callback for CIK

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_asic.h b/drivers/gpu/drm/radeon/radeon_asic.h
index 248da72..05f75f7 100644
--- a/drivers/gpu/drm/radeon/radeon_asic.h
+++ b/drivers/gpu/drm/radeon/radeon_asic.h
@@ -557,5 +557,6 @@
  * cik
  */
 uint64_t cik_get_gpu_clock_counter(struct radeon_device *rdev);
+u32 cik_get_xclk(struct radeon_device *rdev);
 
 #endif