Fix the GE1/1 OptoHybrid SEM core
A long-standing issue with the GE1/1 OptoHybrid firmware was the behavior of the SEM which aims at correcting errors due to SEU. While the correction may have been happening, the counters were not working, rendering any monitoring pointless. This merge request fixes them.
Some of the commits come from !146 after sorting, rebasing, and testing. Some other commits are original.
Address the first part (SEU) of #61, which describes the problem in more detail and with more context.
Tested on test stands for GE1/1 and GE2/1, and deployed in production at P5.