Bump Chisel to 6.7.0

This is required for the new Chisel annotations API:
chipsalliance/chisel#4643

Author: tymcauley

Diff for: build.sc

@@ -12,7 +12,7 @@ object v {
   val scala = "2.13.12"
   // the first version in this Map is the mainly supported version which will be used to run tests
   val chiselCrossVersions = Map(
-    "5.1.0" -> (ivy"org.chipsalliance::chisel:5.1.0", ivy"org.chipsalliance:::chisel-plugin:5.1.0"),
+    "6.7.0" -> (ivy"org.chipsalliance::chisel:6.7.0", ivy"org.chipsalliance:::chisel-plugin:6.7.0"),
     // build from project from source
     "source" -> (ivy"org.chipsalliance::chisel:99", ivy"org.chipsalliance:::chisel-plugin:99"),
   )