Add support for Silicon Labs hardware

[silabs-bozont]

Hello!
We at Silicon Labs recently released Arduino support for a number of our boards: https://github.com/SiliconLabs/arduino
This PR adds OneWire support to our Arduino compatible boards.
I've tested it with our boards and a couple of DS18B20 sensors - everything seems to work well.
Let me know if there's any change needed or if you need more info on something!
Thanks!

[silabs-bozont]

@PaulStoffregen can you please take a look at this? Thank you very much in advance!

[wb8wka]

@silabs-bozont any progress here? I merged this in on my of OneWire_direct_gpio.h and *regtype.h. do you have a quick program to test this with? I have a BGM220 explorer board with a DS18B20 on PA0 with a 4.7K pullup to 3.3V for DQ, and power and 3.3v connected.

Thanks

Jeff

[wb8wka]

@silabs-bozont Follow up, I got your code working, the Vcc end of the 4.7K resistor had become disconnected. Both with a test program as well as sending out a BTHOME temp beacon

Thanks!!

[silabs-bozont]

Hey @wb8wka,
Glad it works! :)
We were thinking about including a fork of this library with the Silicon Labs Arduino Core to provide OneWire support until this gets merged. That way users can have OneWire without having to apply this patch/PR.