pinctrl: sirf: save the status in suspend and restore after resuming

this patch saves the status of pinctrl registers and restore them while
resuming. this makes all drivers have coherent status for pinmux after
suspending and resuming.

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