arm64: dts: ls1012a: add thermal monitor node

There is a thermal monitoring unit on ls1012a soc which can
monitor and record the temperature of cores so that appropriate actions
can be taken or alarm the user when the temperature exceeds a programmed
temperature threshold.

Signed-off-by: Tang Yuantian <andy.tang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>