Fix & update SEU monitoring for GEx/1

Description

The SEU monitoring (and possibly feature) has been broken on GE1/1 for years (ever?). That should be fixed as soon as possible (to investigate, for example, #277). While mostly a firmware feature, the software must be adjusted as well for proper control & monitoring.

Possible fixes

1. Update the SEU metrics to the new registers
2. Develop an SEU injection function