axi4: IdIndexer; a single ID does NOT imply no response interleaving

Some slaves may never send R until you process their B.
Thus, while there is no read response interleaving, there
is still interleaving between R and B, which breaks AXI4ToTL.

src/main/scala/uncore/axi4/Parameters.scala

@@ -15,7 +15,7 @@ case class AXI4SlaveParameters(
   nodePath:      Seq[BaseNode] = Seq(),
   supportsWrite: TransferSizes = TransferSizes.none,
   supportsRead:  TransferSizes = TransferSizes.none,
-  interleavedId: Option[Int]   = None) // The device will not interleave read responses
+  interleavedId: Option[Int]   = None) // The device will not interleave responses (R+B)
 {
   address.foreach { a => require (a.finite) }
   address.combinations(2).foreach { case Seq(x,y) => require (!x.overlaps(y), s"$x and $y overlap") }