dma-buf/fence: kerneldoc: remove spurious section header

Commit e941759c ("fence: dma-buf
cross-device synchronization (v18)") had a spurious kerneldoc section
header that caused Sphinx to complain. Fix it.

Fixes: e941759c

 ("fence: dma-buf cross-device synchronization (v18)")

Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1470912480-32304-3-git-send-email-sumit.semwal@linaro.org