media: dt-bindings: aspeed-video: Add missing memory-region property

Missed documenting this property in the initial commit.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/devicetree/bindings/media/aspeed-video.txt

@@ -14,6 +14,11 @@ Required properties:
 			the VE
  - interrupts:		the interrupt associated with the VE on this platform
 
+Optional properties:
+ - memory-region:
+	phandle to a memory region to allocate from, as defined in
+	Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+
 Example:
 
 video-engine@1e700000 {
@@ -23,4 +28,5 @@ video-engine@1e700000 {
     clock-names = "vclk", "eclk";
     resets = <&syscon ASPEED_RESET_VIDEO>;
     interrupts = <7>;
+    memory-region = <&video_engine_memory>;
 };