thermal: rcar_gen3_thermal: Remove unneeded curly brackets

When devm_add_action() was turned into devm_add_action_or_reset() the
curly brackets for the error case where kept but are not needed, remove
them to match the style of the driver.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200212224732.736785-1-niklas.soderlund+renesas@ragnatech.se