I2C/IIC working on RPI4

[Elwood Downey]

Yes yes yes!!

I've been trying everything to get I2C working since I started using
freebsd on rpi a few years ago. With this change to config.txt, my hamclock
<https://clearskyinstitute.com/ham/HamClock> project can finally access all
the I2C devices. Now that everything works I will also submit hamclock as a
new package.

Many thanks to everyone for all their work.

Elwood Downey, WB0OEW
Tucson AZ