arm64: dts: fsl-ls1088a-ten64: change to low case hex value

Change to low case for hex value to fix below warning:

arch/arm64/boot/dts/freescale/fsl-ls1088a-ten64.dtb: flash@0:
    partitions: Unevaluated properties are not allowed ('partition@5C0000' was unexpected)

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