Changed minstret to (hopefully) correctly count retired instructions.

Created by: silabs-oysteink

Halting EX stage in case of minstret/h read in EX and any valid instruction in WB. Halting to get correct value for reading minstret to GPR.

No errors for CSR minstret checks in ci_check.

Not SEC clean

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