MPC8349EMDS: Add PCI Agent (PCISLAVE) support

Add the ability for the MPC8349EMDS to run in PCI Agent mode, acting as a
PCI card rather than a host computer.

Signed-off-by: Ira W. Snyder <iws@ovro.caltech.edu>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>