tile: remove global Field ResetVectorBits

Reset vector width is determined by systemBus.busView.
Also move some defs from HasCoreParameters to HasTileParameters.

src/main/scala/tile/FPU.scala

@@ -232,7 +232,7 @@ object FType {
 
 trait HasFPUParameters {
   val fLen: Int
-  val xLen: Int
+  def xLen: Int
   val minXLen = 32
   val nIntTypes = log2Ceil(xLen/minXLen) + 1
   val floatTypes = FType.all.filter(_.ieeeWidth <= fLen)