EEPROM support for Massdrop arm_atsam (CTRL & ALT)

[helluvamatt]

Per the datasheet for ATSAMD51J18A the MCU has a SmartEEPROM function that allows up to 64K of EEPROM storage.

I am working on implementing this in tmk_core/common/arm_atsam/eeprom.c as that file is already set up to handle eeprom simulation in memory and it should be fairly simple to configure SmartEEPROM.

[drashna]

Well, check out the STM stuff too. I think that has some of the same limitations/issues that ATSAM has, so it would be a good place to look.

[tprk77]

I've been watching this ticket, can I offer to help in some way?

[drashna]

There is a PR that adds persistent storage. So it maybe worth checking that out.

[daltona]

Well I'm sorry I missed this issue, but my implementation is actually implementing SmartEEPROM support, with a fallback to original functionality if SmartEEPROM is not enabled on the chip.
Enabling SmartEEPROM can be done with a change that I've made to mdloader, referenced in #6068
So for sure I believe it exactly solves this issue.

[zvecr]

Fixed with 6068.