Updated aliasing of mpp and mpie between mcause and mstatus.

Created by: silabs-oysteink

RVFI didn't always get the correct write values, and the aliasing was only working from mcause to mstatus and not the other way.

The three bits are now duplicated in both mcause and mstatus, and are always written simultaneously. Assertions are added to check that mcause and mstatus always write at the same time, and that the *_rdata.mpp/mpie fields are always the same.

SEC clean

Signed-off-by: Oystein Knauserud Oystein.Knauserud@silabs.com