bcache: Kill op->replace

This is prep work for converting bch_btree_insert to
bch_btree_map_leaf_nodes() - we have to convert all its arguments to
actual arguments. Bunch of churn, but should be straightforward.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

diff --cc drivers/md/bcache/btree.c
Simple merge

diff --cc drivers/md/bcache/btree.h
Simple merge

diff --cc drivers/md/bcache/journal.c
Simple merge

diff --cc drivers/md/bcache/movinggc.c
Simple merge

diff --cc drivers/md/bcache/request.c
Simple merge

diff --cc drivers/md/bcache/request.h
Simple merge

diff --cc drivers/md/bcache/writeback.c
Simple merge