Pipeline flush for JVT writes

Created by: silabs-oysteink

When JVT is being written in WB, all stages are halted until the write is done. A pipeline flush and refetch of PC+4 is then performed to ensure any table jumps in the pipeline will use the correct JVT value.

SEC clean when ZC_EXT=0 Not SEC clean when ZC_EXT=1 due to different halt/flush conditions.

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