block: Convert drivers to immutable biovecs

Now that we've got a mechanism for immutable biovecs -
bi_iter.bi_bvec_done - we need to convert drivers to use primitives that
respect it instead of using the bvec array directly.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: NeilBrown <neilb@suse.de>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com

diff --cc drivers/block/umem.c
Simple merge

diff --cc drivers/md/dm-crypt.c
Simple merge

diff --cc drivers/md/dm-io.c
Simple merge

diff --cc drivers/md/dm-raid1.c
Simple merge

diff --cc drivers/md/dm-verity.c
Simple merge

diff --cc fs/bio.c
Simple merge

diff --cc include/linux/dm-io.h
Simple merge