ARM: dts: atlas7: add pinctrl and gpio descriptions

This patch adds pinctrl and gpio stuff according to the atlas7
pinctrl driver.
Signed-off-by: NWei Chen <Wei.Chen@csr.com>
Signed-off-by: NBarry Song <Baohua.Song@csr.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>