pinctrl: altas7: add sd9 function mux support

The sd9 pin mux with sd3 and it is selected by SYS2PCI_SDIO9SEL.
This makes the codes ugly since the register is not in pinctrl
module.

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