drm/radeon/dpm: add pre/post_set_power_state callbacks (6xx-eg)

For r6xx-evergreen, they are no-ops as they don't support
any dynamic state adjustment.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/r600_dpm.c b/drivers/gpu/drm/radeon/r600_dpm.c
index c9f9647..bcb1967c 100644
--- a/drivers/gpu/drm/radeon/r600_dpm.c
+++ b/drivers/gpu/drm/radeon/r600_dpm.c
@@ -662,6 +662,16 @@
 	r600_dynamicpm_enable(rdev, false);
 }
 
+int r600_dpm_pre_set_power_state(struct radeon_device *rdev)
+{
+	return 0;
+}
+
+void r600_dpm_post_set_power_state(struct radeon_device *rdev)
+{
+
+}
+
 bool r600_is_uvd_state(u32 class, u32 class2)
 {
 	if (class & ATOM_PPLIB_CLASSIFICATION_UVDSTATE)