dma-buf/sync_file: Fix docs syntax

dma-buf/sync_file: Fix docs syntax

[ Upstream commit 05d56d8079d510a2994039470f65bea85f0075ee ]

Fixes the warning:

  include/uapi/linux/sync_file.h:77: warning: Function parameter or member 'num_fences' not described in 'sync_file_info'

Fixes: 2d75c88fefb2 ("staging/android: refactor SYNC IOCTLs")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20230724145000.125880-1-robdclark@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>