arm64: dts: renesas: r8a77980: add thermal support

Describe THS/CIVM in the R8A77980 device trees.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>