Adjust remaining length.

This is not strictly needed since the value isn't used after this point.
However, when temporary debugging is added to the code it is helpful for
this valud to be accurate. Adding it in to avoid future confusion.

lib/asn1.js

@@ -614,6 +614,7 @@ function _fromDer(bytes, remaining, depth, options) {
       }
     } else {
       value = bytes.getBytes(length);
+      remaining -= length;
     }
   }