uboot-imx

IXP: enable RTS

enables the RTS signal with CONFIG_SERIAL_RTS_ACTIVE.
No handshaking is done, but the active RTS signal allows to
connect to the target using a PC which is using RTS/CTS
handshake, and does no harm if the PC is set to ignore RTS.

Signed-off-by: Michael Schwingen <michael@schwingen.org>