Add qemu_cortex_m0/m0+ board.

[zephyrbot]

Reported by Benjamin Walsh:

As an ARM kernel developer, I would like to be able to quickly test/sanitize my Cortex-M0/M0+ code.

AFAIK, there is no QEMU Cortex-M0/M0+ model. However, Cortex-M0/M0+ code should run on an M3. It should be possible to configure the qemu_cortex_m3 board so that it uses the Cortex-M0/M0+ build and configuration instead of the Cortex-M3 one.

(Imported from Jira ZEP-1198)

[zephyrbot]

by XiaoHua Yang:

http://gnuarmeclipse.github.io/qemu/

[galak]

Cortex-M0/0+ support is now in qemu and we can enable this on bbc_microbit if we desire.

@ioannisg & @carlescufi thoughts on enabling qemu on bbc_microbit?

[ioannisg]

@galak it would be great, actually. Should we arrange to have this for 2.1.0?