drm/amd: Fix a few more NULL pointer dereference in device cleanup

drm/amd: Fix a few more NULL pointer dereference in device cleanup

I found a few more paths that cleanup fails due to a NULL version pointer
on unsupported hardware.

Add NULL checks as applicable.

Fixes: 39fc2bc4da00 ("drm/amdgpu: Protect GPU register accesses in powergated state in some paths")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f5a05f8414fc10f307eb965f303580c7778f8dd2)
Cc: stable@vger.kernel.org