Add support for HSE Oscillator in stm32g0

[cbruiz]

HSE oscillator support

[Dirbaio]

This PR has 3 things in one. Could you do just the "add HSE oscillator support" changes?

• Why is w.set_nssp(false); required? It only has an effect when using hardware NSS mode, while our driver always uses software NSS mode.
• The example is a bit niche IMO, we already have examples hsowing how to use USB and SPI. I don't think adding an example showing how to use SPI and USB at the same time is worth it.

[cbruiz]

@Dirbaio I do agree with the observations. It's a bit confusing because initially my PR was motivated with the exploration of the issue #2166. Definitively, the HSE Oscillator support is the only clear missing thing.

[Dirbaio]

thank you!