mcu: Add Kconfig for ATSAME51G19

[EllaFoxo]

This feels like an easy win as the SAME51x chain is already in place. Adds support for the G19 variant found on the Duet Revo Roto toolboard.

[KevinOConnor]

Thanks. Seems fine to me. Just so I understand, have you been able to test this on an actual chip?

-Kevin

[EllaFoxo]

I have not, as I'm developing for the chip, but not the Duet Revo Toolbiard. The chip is identical in flash size and memory to the bigger brother 64 VQFN (J19A). Only difference between these two are fewer pins and fewer PWM+clock channels. The chip itself is the perfect candidate to sit at the crossroads between Klipper and RRF (RP2040 does not count imo). Hence why I would like support for it.

[KevinOConnor]

Thanks. However, I didn't understand your last message. Just for my understanding, have you successfully tested this PR on an ATSAME51G19 chip?

-Kevin