armv8/ls2085a: Update LS2085a PCIe compatible

Compatible field "fsl,20851a-pcie" is not correct.
So update it to "fsl,ls2085a-pcie"

Signed-off-by: Minghuan Lian <Minghuan.Lian at freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar at freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>