Peripheral drivers should validate configuration before applying it to hardware

[bugadani]

apply_config is fallible, which means two things:

• It can fail
• The user can ignore the failure and keep using the driver

Because of this, we should validate the whole configuration before we apply it to the hardware. I don't consider this a blocking issue, although we might want to get it right before the release.

[playfulFence]

When this issue is resolved, we must not forget to add the appropriate # Errors entries (see related FIXMEs in this PR).

[MabezDev]

On further reflection, and a push from @playfulFence I think this is indeed something we want to get it sooner rather than later, for example we can set the baud to a billion bps, and apply_config will happily try to do it.