[LiteX] Add support for ZPU / ZPUino in MiSoC

[mithro]

Brief explanation

MiSoC currently supports the lm32 and mor1k architectures. It would be nice if it also support the ZPU soft core (and the ZPUino peripherals).

Expected results

MiSoC is able to use a CPU core which supports the ZPUino architecture as an option when building SoC components.

Detailed Explanation

ZPU - The Zylin ZPU

ZPUino is a SoC (System-on-a-Chip) based on Zylin's ZPU 32-bit processor core.

The worlds smallest 32 bit CPU with GCC toolchain.

The ZPU is a small CPU in two ways: it takes up very little resources and the architecture itself is small. The latter can be important when learning about CPU architectures and implementing variations of the ZPU where aspects of CPU design is examined. In academia students can learn VHDL, CPU architecture in general and complete exercises in the course of a year.

Further reading

• https://github.com/m-labs/misoc
• https://en.wikipedia.org/wiki/ZPU_(microprocessor)
• https://github.com/zylin/zpu