Move cpu_thermal node from soc node to root node.

cpu_thermal node does not have any register properties and thus
shouldn't be placed on the bus.

This fixes the following build warnings with W=1:

arch/arm64/boot/dts/freescale/fsl-ls1088a-qds.dtb: Warning (simple_bus_reg): Node /soc/thermal-zones missing or empty reg/ranges property
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>