drm/radeon/si: drop cg_update from dpm code

I'm not entirely sure this is required and it won't work
with the dpm restructing anyway.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
index a36736d..e3a9fc7 100644
--- a/drivers/gpu/drm/radeon/si.c
+++ b/drivers/gpu/drm/radeon/si.c
@@ -5210,8 +5210,8 @@
 		WREG32(HDP_MEM_POWER_LS, data);
 }
 
-void si_update_cg(struct radeon_device *rdev,
-		  u32 block, bool enable)
+static void si_update_cg(struct radeon_device *rdev,
+			 u32 block, bool enable)
 {
 	if (block & RADEON_CG_BLOCK_GFX) {
 		si_enable_gui_idle_interrupt(rdev, false);