block/rnbd-srv: Add sanity check and remove redundant assignment

The bio->bi_iter.bi_size is updated when bio_add_page() is called. So we
do not need to assign msg->bi_size again to it, since its redudant and
can also be harmful. Instead we can use it to add a sanity check, which
checks the locally calculated bi_size, with the one sent in msg.

Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Grzegorz Prajsner <grzegorz.prajsner@ionos.com>
Link: https://lore.kernel.org/r/20240809135346.978320-1-haris.iqbal@ionos.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>