ARM: shmobile: use __iomem pointers for MMIO

ARM is moving to stricter checks on readl/write functions,
so we need to use the correct types everywhere.

This patch is a bit ugly for shmobile, which is the only platform
that just uses integer literals all over the place, but I can't
see a better way to do this.

Acked-by: Simon Horman <horms@verge.net.au>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: linux-sh@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>