[media] stih-cec.txt: document new hdmi phandle

Update the bindings documentation with the new hdmi phandle.
Signed-off-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/devicetree/bindings/media/stih-cec.txt

@@ -9,6 +9,7 @@ Required properties:
  - pinctrl-names: Contains only one value - "default"
  - pinctrl-0: Specifies the pin control groups used for CEC hardware.
  - resets: Reference to a reset controller
+ - hdmi-phandle: Phandle to the HDMI controller
 
 Example for STIH407:
 
@@ -22,4 +23,5 @@ sti-cec@094a087c {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_cec0_default>;
 	resets = <&softreset STIH407_LPM_SOFTRESET>;
+	hdmi-phandle = <&hdmi>;
 };