Bug fix in pre/post trigger counters, was counting even if no valid data out of sync fifo. Clear of WB cyc when FSm is IDLE

git-svn-id: http://svn.ohwr.org/fmc-adc-100m14b4cha/trunk@55 ddd67a1a-c8ad-4635-afe9-0b8a11d8f8e4