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/uncore/tilelink2/Crossing.scala

@@ -4,7 +4,7 @@ package uncore.tilelink2
 
 import Chisel._
 import chisel3.internal.sourceinfo.SourceInfo
-import junctions._
+import util._
 
 class TLAsyncCrossing(depth: Int = 8, sync: Int = 3) extends LazyModule
 {

src/main/scala/uncore/tilelink2/RegField.scala

@@ -4,7 +4,7 @@ package uncore.tilelink2
 
 import Chisel._
 import chisel3.util.{Irrevocable, IrrevocableIO}
-import uncore.util.{SimpleRegIO}
+import util.{SimpleRegIO}
 
 case class RegReadFn private(combinational: Boolean, fn: (Bool, Bool) => (Bool, Bool, UInt))
 object RegReadFn

src/main/scala/uncore/tilelink2/RegisterCrossing.scala

@@ -4,8 +4,7 @@ package uncore.tilelink2
 
 import Chisel._
 import chisel3.util.{Irrevocable, IrrevocableIO}
-import junctions._
-import uncore.util.{AsyncResetRegVec}
+import util.{AsyncResetRegVec, AsyncQueue, AsyncScope}
 
 // A very simple flow control state machine, run in the specified clock domain
 class BusyRegisterCrossing(clock: Clock, reset: Bool)