ppc4xx: Change inbound PCIe location for endpoint tests on Katmai

On Yucca & Katmai, the inbound memory map pointed to 0x4.0000.0000, which
is the internal SRAM. Since I now ported and tested this endpoint mode
on Kilauea successfully to map to 0 (SDRAM), I also changed this for
Katmai.

Yucca will stay at internal SRAM for now. Not sure if somebody relies on
this setup.

Signed-off-by: Stefan Roese <sr@denx.de>