pinctrl: sirf: add lost atlas6 uart0-no-stream-control pingroup

the old codes defined uart0_nostreamctrl_pins, but missed pingroup
and padmux definition for it. 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>