drm/amdgpu: drop userq fence driver refs out of fence process()

drm/amdgpu: drop userq fence driver refs out of fence process()

amdgpu_userq_wait_ioctl() takes extra references on waited-on fence
drivers and stores them in waitq->fence_drv_xa. When a new userq fence is
created, those references are transferred into userq_fence->fence_drv_array
so they can be released when the fence completes.

However, those inherited references are currently only dropped from
amdgpu_userq_fence_driver_process(). If a fence never reaches that path,
such as it is already signaled when created, so we need to explicitly release
those fences in that case.

v2: use a list(list_cut_before) for managing the signal userq driver fences.(Christian)
Link: https://patchwork.freedesktop.org/patch/718078/?series=164763&rev=2
v3: Doesn't cache the userq first unsignaled fence and use the cut before list
    head directly.(Christian)

Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>