implement mfii_scsi_cmd_io for handling actual io. previously i got

implement mfii_scsi_cmd_io for handling actual io. previously i got
away with being lazy and just passing everything to the vanilla
scsi cdb path.

sending io via the cdb path with chained sgls seems to trigger a
firmware fault on the new invader boards. sending the same io via
the ldio path works fine though.

tested on invader and thunderbolt boards:

mfii0 at pci1 dev 0 function 0 "Symbios Logic MegaRAID SAS3108" rev 0x02: msi
mfii0: "PERC H730 Mini", firmware 25.2.1.0037, 1024MB cache

mfii0 at pci1 dev 0 function 0 "Symbios Logic MegaRAID SAS2208" rev 0x05: msi
mfii0: "PERC H710 Mini", firmware 21.3.0-0009, 512MB cache

ok jmatthew@