pinctrl: at91: convert __raw to endian agnostic IO

Use endian agnostic _relaxed IO accessors instead of the __raw ones.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Andrew Victor <linux@maxim.org.za>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>