cpu: fix case with o3 cpu blocking and unblocking decode in cycle

cpu: fix case with o3 cpu blocking and unblocking decode in cycle

Fix a case in the O3 CPU where the decode stage blocks and unblocks in a
single cycle sending both signals to fetch which causes an assert or worse.
The previous check could never work before since the status was set to Blocked
before a test for the status being Unblocking was executed.