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

 from drivers/block/drbd/drbd_nl.c:24:
 drivers/block/drbd/drbd_nl.c: In function ‘drbd_adm_attach’:
 drivers/block/drbd/drbd_nl.c:1968:10: warning: implicit conversion from ‘enum drbd_state_rv’ to ‘enum drbd_ret_code’ [-Wenum-conversion]
 drivers/block/drbd/drbd_nl.c:930: warning: Function parameter or member 'flags' not described in 'drbd_determine_dev_size'
 drivers/block/drbd/drbd_nl.c:930: warning: Function parameter or member 'rs' not described in 'drbd_determine_dev_size'
 drivers/block/drbd/drbd_nl.c:1148: warning: Function parameter or member 'dc' not described in 'drbd_check_al_size'

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/20210312105530.2219008-12-lee.jones@linaro.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>