drm/amdgpu: fix possible fence leaks from job structure

drm/amdgpu: fix possible fence leaks from job structure

If we don't end up initializing the fences, free them when
we free the job.  We can't set the hw_fence to NULL after
emitting it because we need it in the cleanup path for the
submit direct case.

v2: take a reference to the fences if we emit them
v3: handle non-job fence in error paths

Fixes: db36632ea51e ("drm/amdgpu: clean up and unify hw fence handling")
Reviewed-by: Jesse Zhang <Jesse.Zhang@amd.com> (v1)
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>