drm/amdgpu: fix uvd crash on Polaris12 during driver unloading

There was a change(below) target for such issue:
d82e2c24 ("drm/amdgpu: Fix crash on device remove/driver unload")
But the fix for VI ASICs was missing there. This is a supplement for
that.

Fixes: d82e2c24 ("drm/amdgpu: Fix crash on device remove/driver unload")

Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>