docs/system: riscv: Add documentation for 'microchip-icicle-kit' machine

This adds the documentation to describe what is supported for the
'microchip-icicle-kit' machine, and how to boot the machine in QEMU.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210322075248.136255-2-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
2 files changed