ARM: nomadik: use __iomem pointers for MMIO

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

Acked-by: Alessandro Rubini <rubini@unipv.it>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: STEricsson <STEricsson_nomadik_linux@list.st.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>