stm32vldiscovery: Add the STM32VLDISCOVERY Machine

stm32vldiscovery: Add the STM32VLDISCOVERY Machine

This is a Cortex-M3 based machine. Information can be found at:
https://www.st.com/en/evaluation-tools/stm32vldiscovery.html

Signed-off-by: Alexandre Iooss <erdnaxe@crans.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210617165647.2575955-3-erdnaxe@crans.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>