jtag: Apply Martin Strubel JTAG implementation for ZPU

jtag: Apply Martin Strubel JTAG implementation for ZPU

The current JTAG debugging capable ZPU implementation (VHDL) consists of:

- A generic, device independent JTAG module (tck, tms, tdi, tdo, trst)
- A TAP module, defining JTAG instruction and data registers
- A few control lines to/from the core (request, execute, acknowledge, ready)
  and:
  * An emulation instruction register
  * A data exchange register
- An enhanced ZPU small core state machine