Add support for DACC module

[haata]

There aren't a lot of examples yet (other than simple ones like this: https://github.com/stm32-rs/stm32f4xx-hal/blob/master/src/dac.rs) for MCU DACs (probably because they aren't a super common hardware feature).

Ideally this should support PDC supplied data clocked in using a TC timer. Which should allow for things such as sounds for a speaker.