thermal: rcar_thermal: fix duplicate IRQ request

The driver on R8A77995 requests the same IRQ twice since
platform_get_resource() is always called for the 1st IRQ resource.

Fixes: 1969d9dc ("thermal: rcar_thermal: add r8a77995 support")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>