media: dt-bindings: media: add "hisilicon,hi3796cv300-ir" compatible

It documents "hisilicon,hi3796cv300-ir" compatible for Hi3796CV300 IR
device.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/devicetree/bindings/media/hix5hd2-ir.txt

 Device-Tree bindings for hix5hd2 ir IP
 
 Required properties:
-	- compatible: Should contain "hisilicon,hix5hd2-ir".
+	- compatible: Should contain "hisilicon,hix5hd2-ir", or:
+		- "hisilicon,hi3796cv300-ir" for Hi3796CV300 IR device.
 	- reg: Base physical address of the controller and length of memory
 	  mapped region.
 	- interrupts: interrupt-specifier for the sole interrupt generated by