drm/amdgpu/powerplay: enable sysfs and debugfs interfaces late

BugLink: http://bugs.launchpad.net/bugs/1546572

To avoid users accessing them before the module has finished
initializing them and make sure they are only created if
dpm has properly initialized.
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 898b1dea)
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_powerplay.c

@@ -130,6 +130,10 @@ static int amdgpu_pp_late_init(void *handle)
 		ret = adev->powerplay.ip_funcs->late_init(
 					adev->powerplay.pp_handle);
 
+#ifdef CONFIG_DRM_AMD_POWERPLAY
+	if (adev->pp_enabled)
+		amdgpu_pm_sysfs_init(adev);
+#endif
 	return ret;
 }
 
@@ -144,7 +148,6 @@ static int amdgpu_pp_sw_init(void *handle)
 
 #ifdef CONFIG_DRM_AMD_POWERPLAY
 	if (adev->pp_enabled) {
-		amdgpu_pm_sysfs_init(adev);
 		if (amdgpu_dpm == 0)
 			adev->pm.dpm_enabled = false;
 		else