drm/amdgpu/vcn: add a helper framework for engine resets

With engine resets we reset all queues on the engine rather
than just a single queue.  Add a framework to handle this
similar to SDMA.

Reviewed-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Tested-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>