Fix boot controller finding logic for the C8220

In order to boot properly when we want to use both the on-board
AHCI controller (for the OS) and an LSO9205 (for external SATA
storage).  We need to do this because one of the expansion slots is
hanging off a lower PCI address than the baked-in AHCI controller on
the C8220.
Merge pull request #144 from VictorLowther/pull-req-release-mesa-1.6-master-97e8c617fb56435ed75b392677ff9eb4a5d8b398

DE1326: Fix misdetected boot device on C8220 when using both AHCI and LSI controllers. [1/1]