block: Convert some code to bio_for_each_segment_all()

block: Convert some code to bio_for_each_segment_all()

More prep work for immutable bvecs:

A few places in the code were either open coding or using the wrong
version - fix.

After we introduce the bvec iter, it'll no longer be possible to modify
the biovec through bio_for_each_segment_all() - it doesn't increment a
pointer to the current bvec, you pass in a struct bio_vec (not a
pointer) which is updated with what the current biovec would be (taking
into account bi_bvec_done and bi_size).

So because of that it's more worthwhile to be consistent about
bio_for_each_segment()/bio_for_each_segment_all() usage.

Signed-off-by: Kent Overstreet <[email protected]>
CC: Jens Axboe <[email protected]>
CC: NeilBrown <[email protected]>
CC: Alasdair Kergon <[email protected]>
CC: [email protected]
CC: Alexander Viro <[email protected]>