Move a bunch more things into util package

A lot of utility code was just being imported willy-nilly from one
package to another. This moves the common code into util to make things
more sensible. The code moved were

 * The AsyncQueue and AsyncDecoupledCrossing from junctions.
 * All of the code in rocket's util.scala
 * The BlackBox asynchronous reset registers from uncore.tilelink2
 * The implicit definitions from uncore.util

src/main/scala/rocket/dcache.scala

@@ -7,10 +7,10 @@ import junctions._
 import uncore.tilelink._
 import uncore.agents._
 import uncore.coherence._
-import uncore.util._
 import uncore.constants._
+import uncore.util._
+import util._
 import cde.{Parameters, Field}
-import Util._
 
 class DCacheDataReq(implicit p: Parameters) extends L1HellaCacheBundle()(p) {
   val addr = Bits(width = untagBits)