pinctrl: sirf: fix the pin number and mux bit for usp0

we missed a pin and related mux bit for usp pin group, this
patch fixes it.

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