Add initial RTL

Created by: ganoam

• Accelerator Interconnect module (src/acc_interconnect.sv) Implements one hierarchy level of the the accelerator interconnect

• Accelerator Adapter module (src/acc_adapter.sv) Adapter between acc-agnostic offloading X-interface and accelerator C-interface

• Accelerator Predecoder module (src/acc_predecoder.sv) Per-extension instruction metadata predecoder

• Accelerator X/C/(PRD) interface definitions (src/acc_intf.sv)

• X/C- Interface / struct assignment and typedef macros (src/acc_interface/assign/typedef.sh)

Signed-off-by: ganoam gnoam@live.com