arm64: dts: freescale: ls1028a: Remove undocumented 'fsl,ls-pcie-ep'

Remove the undocumented compatible string 'fsl,ls-pcie-ep' property from
the ls1028a device tree source to fix DTB_CHECK warnings.

arch/arm64/boot/dts/freescale/fsl-ls1028a-rdb.dtb: pcie-ep@3400000: compatible: ['fsl,ls1028a-pcie-ep', 'fsl,ls-pcie-ep'] is too long
	from schema $id: http://devicetree.org/schemas/pci/fsl,layerscape-pcie-ep.yaml#



Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>