ARM: dts: at91: sama7g5: add nodes for video capture

Add node for the XISC (eXtended Image Sensor Controller) and CSI2DC
(csi2 demux controller).
These nodes represent the top level of the video capture hardware pipeline
and are directly connected in hardware.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220503095127.48710-4-eugen.hristev@microchip.com