dma-buf/sw-sync: Fix the is-signaled test to handle u32 wraparound

dma-buf/sw-sync: Fix the is-signaled test to handle u32 wraparound

Use the canonical __dma_fence_is_later() to compare the fence seqno
against the timeline seqno to check if the fence is signaled.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170629125930.821-2-chris@chris-wilson.co.uk