power/reset/rmobile-reset.c: Fix !HAS_IOMEM build

Fixes:
drivers/power/reset/rmobile-reset.c: In function ‘rmobile_reset_probe’:
drivers/power/reset/rmobile-reset.c:61:2: error: implicit declaration of function ‘iounmap’ [-Werror=implicit-function-declaration]
  iounmap(sysc_base2);

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Sebastian Reichel <sre@kernel.org>