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
If a device has configurable bus-width, we need a stable way of
enumerating registers. The byte offset stays unchanged.
This change also makes it possible to put an arbitrary number of RegFields
starting at some address which are then chopped up into appropriately bus-
sized registers.
The implementation unconditionally drove the register.
This made it incompatible with drivers from the device itself.
Besides, writing only parts of a register at a time is ultra-shady.
