i.MX6DL does not have the second IPU, but the LVDS multiplexers can connect
either LVDS channel of the LDB to IPU1 DI0 or IPU1 DI1.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
[shawn.guo: remove "crtcs" property from imx6qdl.dtsi]
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>