drm/radeon/dpm: implement force performance level for SI

Allows you to force the selected performance level via sysfs.

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 2bacc77..7efa51a 100644
--- a/drivers/gpu/drm/radeon/radeon_asic.h
+++ b/drivers/gpu/drm/radeon/radeon_asic.h
@@ -683,6 +683,8 @@
 void si_dpm_display_configuration_changed(struct radeon_device *rdev);
 void si_dpm_debugfs_print_current_performance_level(struct radeon_device *rdev,
 						    struct seq_file *m);
+int si_dpm_force_performance_level(struct radeon_device *rdev,
+				   enum radeon_dpm_forced_level level);
 
 /* DCE8 - CIK */
 void dce8_bandwidth_update(struct radeon_device *rdev);