ARM: davinci: aintc: use writel_relaxed()

Raplace all calls to __raw_writel() with writel_relaxed().
It's safe to do as there's no endianness conversion being
done in the code.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>