drm/amdgpu/pm: look up current_level for asics without pm callback

For asics without a callback, use the current level rather than 0xff.
This can avoid an unnecesary forced level set on older asics when
set by the user.
Reviewed-by: Kevin Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/amdgpu_pm.c

@@ -310,7 +310,7 @@ static ssize_t amdgpu_set_power_dpm_force_performance_level(struct device *dev,
 	struct amdgpu_device *adev = drm_to_adev(ddev);
 	const struct amd_pm_funcs *pp_funcs = adev->powerplay.pp_funcs;
 	enum amd_dpm_forced_level level;
-	enum amd_dpm_forced_level current_level = 0xff;
+	enum amd_dpm_forced_level current_level;
 	int ret = 0;
 
 	if (amdgpu_in_reset(adev))
@@ -350,6 +350,8 @@ static ssize_t amdgpu_set_power_dpm_force_performance_level(struct device *dev,
 
 	if (pp_funcs->get_performance_level)
 		current_level = amdgpu_dpm_get_performance_level(adev);
+	else
+		current_level = adev->pm.dpm.forced_level;
 
 	if (current_level == level) {
 		pm_runtime_mark_last_busy(ddev->dev);