Configure GPIOx_ASCR register for STM32L47x/STM32L48x

[jspngh]

I've spent some time figuring out why the ADC does not work on my STM32L476 board.
Turns out it is because of this little remark in the reference manual:

Right now I added it directly in the into_analog function, but maybe it should be placed in a separate function?

[jspngh]

Seems like for stm32l4x5 the ascr register will only be available in stm32-rs v0.15.0
Maybe this PR can be delayed until that is released.

[MathiasKoch]

Seems like for stm32l4x5 the ascr register will only be available in stm32-rs v0.15.0 Maybe this PR can be delayed until that is released.

I did the PR that fixed this in stm32-rs and the yet-to-be-released is the reason i have not opened this PR before 👍

But thank you very much for you contribution! I think we should keep taps on when stm32-rs v0.15.0 is released, and let this PR be dorment until.

[MathiasKoch]

stm32-rs v0.15.0 released: https://github.com/stm32-rs/stm32-rs/releases/tag/v0.15.0 🎉

[jspngh]

Some small things needed to be done to update to the new stm32-rs release.
Updating the PAC should probably be done in a separate PR, but I wanted to let the CI run already to check if there are issues.

[jspngh]

Unsurprisingly, updating to the new stm32-rs release for all devices will be more involved than simply fixing the issues for a single device. I don't know if anyone is already working on this?