thermal,rcar_thermal: Add dependency on HAS_IOMEM

Commit beeb5a1e (thermal: rcar-thermal: Enable driver compilation with COMPILE_TEST)
broke build on archs wihout io memory.

On archs like S390 or um this driver cannot build nor work.
Make it depend on HAS_IOMEM to bypass build failures.

drivers/thermal/rcar_thermal.c:404: undefined reference to `devm_ioremap_resource'
drivers/thermal/rcar_thermal.c:426: undefined reference to `devm_ioremap_resource'

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>