don't use Scala to Chisel implicit conversions outside of rocket

src/main/scala/rocket/rocket.scala

@@ -8,6 +8,7 @@ import uncore.agents.CacheName
 import uncore.constants._
 import junctions.HasAddrMapParameters
 import util._
+import Chisel.ImplicitConversions._
 import cde.{Parameters, Field}
 
 case object XLen extends Field[Int]