arm64: dts: imx8mq: add mipi csi phy and csi bridge descriptions

Describe the 2 available CSI interfaces on the i.MX8MQ with the MIPI-CSI2
receiver (new driver) and the CSI Bridge that provides the user buffers
(existing driver).

An image sensor is to be connected to the MIPIs' second port, to be described
in board files.

Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>