for USP-based UART, we use two gpios as RTS and CST pins.
Signed-off-by: NQipan Li <Qipan.Li@csr.com>
Signed-off-by: NBarry Song <Baohua.Song@csr.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>