Use new pin names containing DCE/DTE for UART RX/TX/RTS/CTS pins, this
is to distinguish the DCE/DTE functions.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>