drm/amdgpu: Add put fence in amdgpu_fence_driver_clear_job_fences

This function should drop the fence refcount when it extracts the
fence from the fence array, just as it's done in amdgpu_fence_process.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>