pci: Allow for PCI addresses to be 64-bit

PCI bus is inherently 64-bit.  While not all system require access to
the full 64-bit PCI address range some do.  This allows those systems
to enable the full PCI address width via CONFIG_SYS_PCI_64BIT.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Andrew Fleming-AFLEMING <afleming@freescale.com>
Acked-by: Wolfgang Denk <wd@denx.de>