mpc83xx: Set PCI I/O bus-address base to zero.

The device trees for these boards describe PCI I/O as starting from
address zero from the device's perspective.

Placing I/O elsewhere may cause problems with certain PCI boards, and may
cause problems with Linux.

Signed-off-by: Scott Wood <scottwood@freescale.com>
diff --git a/include/configs/MPC837XERDB.h b/include/configs/MPC837XERDB.h
index 3b5d035..b2f54e1 100644
--- a/include/configs/MPC837XERDB.h
+++ b/include/configs/MPC837XERDB.h
@@ -366,7 +366,7 @@
 #define CFG_PCI_MMIO_BASE	0x90000000
 #define CFG_PCI_MMIO_PHYS	CFG_PCI_MMIO_BASE
 #define CFG_PCI_MMIO_SIZE	0x10000000 /* 256M */
-#define CFG_PCI_IO_BASE		0xE0300000
+#define CFG_PCI_IO_BASE		0x00000000
 #define CFG_PCI_IO_PHYS		0xE0300000
 #define CFG_PCI_IO_SIZE		0x100000 /* 1M */