Force SB800 bootblock to use I/O for PCI config

Force SB800 bootblock to use I/O for PCI config

If PCI config cycles use MMIO instead of I/O in the bootblock
code the cycles will go nowhere since the MMIO feature hasn't been
configured yet. This change forces the cycles to use I/O.

Change-Id: I93dec45f7cd6764cef7736c774a4d4e61bf7d7e0
Signed-off-by: Marc Jones <marcj303@gmail.com>
Reviewed-on: http://review.coreboot.org/630
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>