pseries: Fix array overrun bug in PCI code

spapr_populate_pci_devices() containd a loop with PCI_NUM_REGIONS (7)
iterations.  However this overruns the 'bars' global array, which only has
6 elements. In fact we only want to run this loop for things listed in the
bars array, so this patch corrects the loop bounds to reflect that.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Andrzej Zaborowski <andrew.zaborowski@intel.com>
