ARM: dts: imx6sx: fix the pad setting for uart CTS_B

The current pinfunc define all uart CTS_B IO port for DCE uart 'CTS_B'
IP port. Since uart IP port 'CTS_B' is output, and it don't need to
set 'SELECT_INPUT' bit.
Signed-off-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>