RVFI - Improving mstatsu_fs reporting and fcsr reporting
Created by: YoannPruvost
This PR corrects two points I previously overlooked
- moved the mstatus_fs reporting trigger for mstatus_we to mstatus_fs_we on APU instructions
- remove the fcsr_we when we have frm_we or fflags_we and use the already in place mechanism when populating rvfi signals to handle the multi csr update