The ColdFire PCI configuration space access functions swap addressing
regions to do their work. Just letting the read/write cycles exit
the CPU core (via the ColdFire "nop" instruction) is not enough to
guarantee that the address region remapping has actually completed.
Insert a read back of the mapping register to be absolutely sure
that the remapping has completed.
This fixes an occasional boot hang during the ColdFire PCI initialization
phase.