ARM: dts: r8a7743: Add thermal device to DT

This patch instantiates the thermal sensor module with thermal-zone
support.

This patch is based on the commit cac68a56
("ARM: dts: r8a7791: enable to use thermal-zone") by Kuninori Morimoto.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>