thermal: rcar: tidyup registration failure case

Current rcar_thermal driver didn't care about rcar_theraml_irq_disable()
when registration failure case on _probe(), and _remove().
And, it returns without unregistering thermal zone when
registration failure case on _probe().
This patch fixes these issue.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>