ARM: DT: imx53: fix lvds channel 1 port

using LVDS channel 1 on an i.MX53 leads to following error:

imx-ldb 53fa8008.ldb: unable to set di0 parent clock to ldb_di1

This comes from imx_ldb_set_clock with mux = 0. Mux parameter must be "1" for
reparenting di1 clock to ldb_di1. The value of the mux param comes from device
tree port settings.

On i.MX5, the internal two-input-multiplexer is used. Due to hardware limitations,
only one port (port@[0,1]) can be used for each channel (lvds-channel@[0,1],
respectively)

Documentation update suggested by Philipp Zabel <p.zabel@pengutronix.de>

Signed-off-by: Markus Niebel <Markus.Niebel@tq-group.com>
Fixes: e05c8c9a ("ARM: dts: imx53: Add IPU DI ports and endpoints, move imx-drm node to dtsi")
Cc: <stable@vger.kernel.org>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>