Don't set XLen in WithRadianceCores

Currently Vortex core uses hardcoded 32-bit xlen in its RTL.  Also, setting this
here breaks instantiating Gemmini, which assumes 64bit.  So just leave it
unchanged and try to treat Vortex as a special-case.

src/main/scala/radiance/subsystem/Configs.scala

@@ -15,7 +15,6 @@ class WithRadianceCores(
   n: Int,
   useVxCache: Boolean
 ) extends Config((site, _, up) => {
-  case XLen => 32
   case TilesLocated(InSubsystem) => {
     val prev = up(TilesLocated(InSubsystem), site)
     val idOffset = prev.size
@@ -53,7 +52,6 @@ class WithFuzzerCores(
   n: Int,
   useVxCache: Boolean
 ) extends Config((site, _, up) => {
-  case XLen => 32
   case TilesLocated(InSubsystem) => {
     val prev = up(TilesLocated(InSubsystem), site)
     val idOffset = prev.size