bcache: Make bch_keylist_realloc() take u64s, not nptrs

Getting away from KEY_PTRS and moving toward KEY_U64s - and getting rid of magic
2s

Also - split out the part that checks against journal entry size so as to avoid
a dependancy on struct cache_set in bset.c

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
index ba02f05..303d31a 100644
--- a/drivers/md/bcache/bset.h
+++ b/drivers/md/bcache/bset.h
@@ -259,7 +259,7 @@
 
 struct bkey *bch_keylist_pop(struct keylist *);
 void bch_keylist_pop_front(struct keylist *);
-int bch_keylist_realloc(struct keylist *, int, struct cache_set *);
+int __bch_keylist_realloc(struct keylist *, unsigned);
 
 void bch_bkey_copy_single_ptr(struct bkey *, const struct bkey *,
 			      unsigned);