block: drbd: drbd_receiver: Demote less than half complete kernel-doc header

block: drbd: drbd_receiver: Demote less than half complete kernel-doc header

Fixes the following W=1 kernel build warning(s):

 drivers/block/drbd/drbd_receiver.c:1641: warning: Function parameter or member 'op' not described in 'drbd_submit_peer_request'
 drivers/block/drbd/drbd_receiver.c:1641: warning: Function parameter or member 'op_flags' not described in 'drbd_submit_peer_request'
 drivers/block/drbd/drbd_receiver.c:1641: warning: Function parameter or member 'fault_type' not described in 'drbd_submit_peer_request'

Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: drbd-dev@lists.linbit.com
Cc: linux-block@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210312105530.2219008-10-lee.jones@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>