Make fsl_sata driver work on P1022

P1022 SATA controller may set the wrong CCR bit for a command completion.
This would previously cause an interrupt storm. Solve this by marking all
commands complete, and letting the end_transaction deal with the successes.
Causes no problems on P5020.

While here, fix a minor bug in collision detection. The Freescale SATA
controller only has 16 slots, not 32.