bcache: Bkey indexing renaming

More refactoring:

node() -> bset_bkey_idx()
end() -> bset_bkey_last()

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h
index 164a7e2..ae66311 100644
--- a/include/uapi/linux/bcache.h
+++ b/include/uapi/linux/bcache.h
@@ -118,7 +118,7 @@
 	return (struct bkey *) (d + bkey_u64s(k));
 }
 
-static inline struct bkey *bkey_last(const struct bkey *k, unsigned nr_keys)
+static inline struct bkey *bkey_idx(const struct bkey *k, unsigned nr_keys)
 {
 	__u64 *d = (void *) k;
 	return (struct bkey *) (d + nr_keys);