* Fixes bug with AXI4 MMIO ports not being generated properly due to
IOBinders issue. Additionally adds IOCells to AXI4 ports so that they
appear in ChipTop
* Change IOBinders to also require passing p: Parameters
to child functions. Serialization of type targets via ClassTags fails
for compound types, so we cannot use `BaseSubsystem with HasSomeTrait`
as the type target in OverrideIOBinders.
863f723708