thermal: rcar_gen3_thermal: Add support for up to five TSC nodes

Add support for up to five TSC nodes. The new THCODE values are taken
from the example in the datasheet.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210309162419.2621359-1-niklas.soderlund+renesas@ragnatech.se