Wrong setting of bias on Galileo Gen 2

[andy-shev]

While comment tells about pull up disable, which is, by the fact, true, it actually enables pull down.
In particular, it might be a glitch for SPI chip select which becomes active, since active low nature and pull down applied.

There are three possible states for GPIO expander that services BIAS setting, i.e.

1. output-high — Pull Up
2. output-low — Pull Down
3. input — Pull Disabled

We need to revisit the settings and make them in accordance with the official guide.