After the previous update to disk_check_events(), nobody is using
non-syncing __disk_block_events().  Remove @sync and, as this makes
__disk_block_events() virtually identical to disk_block_events(),
remove the underscore prefixed version.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>