powerpc: T208xQDS: Compile the legacy PCIe routines conditionally

Compile the legacy PCIe initialization reoutines only when DM_PCI
is not enabled.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>