pinctrl: sirf: fix spinlock deadlock in sirfsoc_gpio_set_input

sirfsoc_gpio_set_input() is called in those functions which have
held the spinlock, so delete the duplicated locking.

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