thermal: rcar: remove __devinitconst

commit 76cc1887 "thermal: rcar: add Device Tree support"
added device tree support for this driver, but also added
an instance of __devinitconst, which is no longer defined

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Zhang Rui <rui.zhang@intel.com>