staging/android: store last signaled value on sync timeline

Now fence timeline is aware of the last signaled fence, as it
receives the increment to the current value in sync_timeline_signal().

That allow us to remove .has_signaled() from timeline_ops as we can
directly compare using timeline->value and fence->seqno in sync.c

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>