pinctrl: sirf: enable GPIO pullup/down configuration from dts

commit 7bec2074 remove sirfsoc_gpio_set_pull function,
this patches takes the feature back by adding sirf,pullups and
sirf,pulldowns prop in dts, and the driver will set the GPIO
pull according to the dts.

Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>