pinctrl: sirf: replace of_gpio_simple_xlate by sirf specific of_xlate

the default of_gpio_simple_xlate() will make us fail while getting gpios
bigger than 32 by of_get_named_gpio() or related APIs.
this patch adds a specific of_xlate callback for sirf gpio_chip and fix
the problem.

Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>