drivers: stepper: fix fake stepper controller cid issues

Fix: Write to const-qualified field. (WRITE_CONST_FIELD)
- #81915, #81920, #81922, #81924, #81932, #81940, #81941
- #81946, #81947, #81959, #81961, #81970, #81973, #81977

Signed-off-by: Jilay Pandya <jilay.pandya@outlook.com>