Expand mdloader to support nvm usage

[drashna]

Specifically, so this PR can be supported, so we can have persistent settings on the ATSAM boards.

qmk/qmk_firmware#6068

[daltona]

https://github.com/daltona/mdloader/tree/enable-smart-eeprom while still Work In Progress, adds an option that will update the NVM user row in order to enable the smart eeprom that is used in the mentioned qmk_firmware.
For those interested to test.

[drashna]

Also, figured I should tag @patrickmt on this.

[robhaswell]

Hi, what's blocking getting this branch merged? If it is real-world testing, can I help? As a user, I think persistent settings should be landed for the Drop boards ASAP.

[aoswalt]

Would love to get an update on this.

[rshutt]

I agree. I really rather not have to maintain a fork of this functionality. I'm guessing others already have?