pci: layerscape: update the searching compatible of LX2160A PCIe

The current fixup of LX2160A PCIe nodes is based on non-production
rev1 silicon, and in Linux the nodes have been updated for rev2
silicon, so update the searching compatible string to match the
kernel changes. And for compatibility with the rev1 nodes, move
forward the board specific fixup.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>