Replicate r242422 from ata(4) to mvs(4):
Only four specific ATA PIO commands transfer several sectors per DRQ block
(interrupt).  All other ATA PIO commands transfer one sector or 512 bytes
at one time.  Hardcode these exceptions in mvs(4) with ATA_CAM option.
This fixes timeout of READ LOG EXT command used by `smartctl -x /dev/adaX`.
Also it fixes timeout of DOWNLOAD_MICROCODE on `camcontrol fwdownload`.