ARM: dts: imx7: Move tempmon node out of bus

Move tempmon node from soc node to root node.

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

This fixes the following build warning with W=1:

arch/arm/boot/dts/imx7d-cl-som-imx7.dtb: Warning (simple_bus_reg): Node /soc/aips-bus@30000000/tempmon missing or empty reg/ranges property

Fixes: de25b9bb

 ("ARM: dts: imx7s: add temperature monitor support")
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>