dt-bindings: pci: layerscape-pci: add compatible strings "fsl,ls1043a-pcie"

The PCIe compatible string for LS1043A was lost, so add it.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>