Easier enumeration of reset-cause

[Ralim]

Hello,
This is just a suggestion, and I couldn't find an existing request.
It would be nice to have a formalised way to get the reset cause in a nicely defined method.

I.e on STM32 we have the upper bits of RCC_CSR that can be read and mapped to the cause of the latest reset of the chip.

Of course if this is already on the roadmap, please feel free to close 🙇🏼

Thank you for the epic work here ❤️