drm/amdgpu: Correct the place of amdgpu_pm_sysfs_fini

The amdgpu_pm_sysfs_fini should call before amdgpu_device_ip_fini,
or the adev->pm.dpm_enabled would be set to 0, then the device files
related to pp won't be removed by amdgpu_pm_sysfs_fini when unload
driver.

Signed-off-by: Emily Deng <Emily.Deng@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>