arm64: dts: imx8mn-evk: Add camera support

Add support for the OV5640 camera.

Tested with the following commands:

media-ctl -l "'ov5640 2-003c':0 -> 'csis-32e30000.mipi-csi':0 [1]"
media-ctl -V "'ov5640 2-003c':0 [fmt:UYVY8_1X16/640x480 field:none]"
media-ctl -V "'crossbar':0 [fmt:UYVY8_1X16/640x480 field:none]"
media-ctl -V "'mxc_isi.0':0 [fmt:UYVY8_1X16/640x480 field:none]"
v4l2-ctl --device /dev/video0 --set-fmt-video=width=640,height=480,pixelformat=YUYV
v4l2-ctl --stream-mmap -d /dev/video0;
gst-launch-1.0 -v v4l2src device=/dev/video0 ! video/x-raw,width=640,height=480 ! waylandsink

Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>