commit af614b23 adds lost USP-based UART pin groups for prima2,
but missed usp1_uart_nostreamctrl group for atlas6, this patch fixes it.

this makes USP(Universal Serial Ports) port1 can work as uart without
stream ctrl.
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>