arch: attiny1634: Use built-in temperature calibration data

[stcarlso]

Improves the out of box thermal calibration of all attiny1634 lights by using the factory calibration data in the Device Signature register.

I do not have enough lights to do a large scale test of this one, but the temperature indicated after factory reset is much closer to the correct value on the two lights I tried (Emisar D1 v2 boost and Emisar D4K 2ch), within 2-3 degrees C.

[SiteRelEnby]

Looks like it gives consistently reasonable results on a couple of my lights.