bcachefs: Refactor __bch2_cut_front()

Minor cleanup - prep work for new key types for reflink

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
diff --git a/fs/bcachefs/extents.h b/fs/bcachefs/extents.h
index fe92737..549188c 100644
--- a/fs/bcachefs/extents.h
+++ b/fs/bcachefs/extents.h
@@ -540,11 +540,11 @@ do {									\
 	}								\
 } while (0)
 
-bool __bch2_cut_front(struct bpos, struct bkey_s);
+void __bch2_cut_front(struct bpos, struct bkey_s);
 
-static inline bool bch2_cut_front(struct bpos where, struct bkey_i *k)
+static inline void bch2_cut_front(struct bpos where, struct bkey_i *k)
 {
-	return __bch2_cut_front(where, bkey_i_to_s(k));
+	__bch2_cut_front(where, bkey_i_to_s(k));
 }
 
 bool bch2_cut_back(struct bpos, struct bkey *);