drbd: turn bitmap I/O comments into regular block comments

drbd: turn bitmap I/O comments into regular block comments

W=1 build warns because the bitmap I/O comments use '/**', which
marks them as kernel-doc comments even though these functions do not
document an external API.

Convert these comments to regular block comments so kernel-doc no
longer parses them.

Signed-off-by: Sukrut Heroorkar <hsukrut3@gmail.com>
Acked-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>