Revert "bio: limit bio max size"

This reverts commit cd2c7545

.

Alex reports that the commit causes corruption with LUKS on ext4. Revert
it for now so that this can be investigated properly.

Link: https://lore.kernel.org/linux-block/1620493841.bxdq8r5haw.none@localhost/
Reported-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
Signed-off-by: Jens Axboe <axboe@kernel.dk>