Run-time failures for DspComplex isLit()

[ucbjrl]

With chipsalliance/chisel#1256 (Fix deprecation warning that leaks into user code), isLit() now calls litOption.isDefined which is explicitly unimplemented for Aggregates and the isLit() tests in DspComplex now blow up with:

[info]   This instance will process DspComplex[Real] numbers with the basic mathematical operations
[info]   - operation + should work for all inputs *** FAILED ***
[info]     firrtl.options.OptionsException: Exception thrown when elaborating ChiselGeneratorAnnotation
[info]     at chisel3.stage.ChiselGeneratorAnnotation.elaborate(ChiselAnnotations.scala:55)
[info]     at chisel3.stage.phases.Elaborate$$anonfun$transform$1.apply(Elaborate.scala:19)
[info]     at chisel3.stage.phases.Elaborate$$anonfun$transform$1.apply(Elaborate.scala:18)
[info]     at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
[info]     at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
[info]     at scala.collection.immutable.List.foreach(List.scala:392)
[info]     at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:241)
[info]     at scala.collection.immutable.List.flatMap(List.scala:355)
file loaded in 0.03255344 seconds, 21 symbols, 11 statements
[info] [0.030] Done elaborating.
[info]     at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:18)
[info]     at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:16)
[info]     ...
[info]     Cause: scala.NotImplementedError: an implementation is missing
[info]     at scala.Predef$.$qmark$qmark$qmark(Predef.scala:230)
[info]     at chisel3.Aggregate.litOption(Aggregate.scala:46)
[info]     at chisel3.Data.isLit(Data.scala:496)
[info]     at dsptools.numbers.DspComplex$.apply(DspComplex.scala:22)

A fix to chisel3 is in progress (chipsalliance/chisel#1277).