[bwn] TX logging / completion fixes

• Log the per-completion status out if requested
• If we get a PHY failure, the retrycnt is set to 0 and ack=0, so the logic was incorrect. So, for ack=0, ensure we don't log a retrycnt of 0 (or rate control breaks) or a negative retrycnt (or rate control also breaks.)

Tested:

• BCM4321 (11abgn N-PHY), BCM4312 (LP-PHY)