dma-fence: Report the composite sync_file status

Same as for the individual fences, we want to report the actual status
of the fence when queried.

Reported-by: Petri Latvala <petri.latvala@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Petri Latvala <petri.latvala@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190812091203.29871-1-chris@chris-wilson.co.uk