pci: layerscape: Suffix API names with _ls

Suffix layerscape fixup API names with _ls.
This is required to organize device tree fixup in common,
layerscape and layerscape_gen4 specific code.

Signed-off-by: Wasim Khan <wasim.khan@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>