Fix bug in storing encoder steps

[reecej]

Fix bug where encoder steps are overwritten each time the board is booted up. This is related to the chain on bottom functionality, although the bug occurs whether the chain is on top or bottom.

[blurfl]

I've tested and confirmed that this works with these use cases:

• upgrading from v1.04 firmware (requires chain cal, as expected) using GCv1.04
• upgrading from v1.05 master before this PR (did not require chain cal) using GCv10.5-master

[krkeegan]

I gather that it wasn't working to call setupAxis() after loading the steps from eeprom?

[reecej]

Correct. When setupAxes() was run, it would read the current encoder position and set the steps to that value, really just to initialize the values. But that was overwriting our loaded previous steps value, and hence the chains were having to be recalibrated at every system boot.

[BarbourSmith]

This works great for me as well. No need to do the chain re-cal 👍 👍 Excellent job tracking down what the issue was!