add new (Tilelink2) RoCC accelerator interface

Includes configuration, test programs, and documentation updates.

src/main/scala/example/Configs.scala

@@ -2,6 +2,10 @@ package example
 
 import config.{Parameters, Config}
 import testchipip.WithSerialAdapter
+import coreplex.WithRoccExample
 
 class DefaultExampleConfig extends Config(
   new WithSerialAdapter ++ new rocketchip.DefaultConfig)
+
+class RoccExampleConfig extends Config(
+  new WithRoccExample ++ new DefaultExampleConfig)