bcachefs: Fix extent_ptr_durability() calculation for erasure coded data

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/extents.c

@@ -723,7 +723,7 @@ static unsigned bch2_extent_ptr_durability(struct bch_fs *c,
 		if (WARN_ON(!s))
 			goto out;
 
-		durability = max_t(unsigned, durability, s->nr_redundant);
+		durability += s->nr_redundant;
 	}
 out:
 	return durability;