ARM: dts: imx6qdl: Move existing MIPI DSI ports into a new 'ports' node

The MIPI DSI node contains some ports which represent possible DRM CRTCs
it can connect with.  Each port has a 'reg' property embedded.  This
property will be wrongly interpretted by the MIPI DSI bus driver, because
the driver will take each subnode which contains a 'reg' property as a
DSI peripheral device.  This patch moves the existing MIPI DSI ports into
a new 'ports' node so that the MIPI DSI bus driver may distinguish its
DSI peripheral device(s) from the existing ports.

Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>