dt-bindings: Update QorIQ TMU thermal bindings

For different types of SoC the sensor id and endianness may vary.
"#thermal-sensor-cells" is used to provide sensor id information.
"little-endian" property is to tell the endianness of TMU.

Signed-off-by: Jia Hongtao <hongtao.jia@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>