thermal: rcar_gen3: Use lowercase hex constants

The style of the driver is to use lowercase hex constants, correct the
few outlines.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20250305174631.4119374-2-niklas.soderlund+renesas@ragnatech.se


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>