added stm32f302x6, stm32f302x8

[sprhawk]

No description provided.

[teskje]

This has also been done in #129, but I suppose it will still take some time until that gets merged, so I'm fine with merging this in the meantime.

I'm curious, have you tested the crate with one of these boards?

[sprhawk]

@ra-kete Yes, I'm running it on an stm32f302r8

[teskje]

Could you add a changelog entry too?
LGTM otherwise.

[sprhawk]

@ra-kete How to write content of Changelog?

Like this?

### Added                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
- added stm32f302x6, stm32f302x8 ([#132](https://github.com/stm32-rs/stm32f3xx-hal/pull/132))                                                                                                                                                                                                                           

[teskje]

Yes, just put it under the existing Added entries under the Unreleased version.
For wording you look at what's there for adding support for new devices in older versions. Something like "Support for stm32f302x6 and stm32f302x8 devices".

[sprhawk]

@ra-kete added to changelog