dt-bindings: display/ingenic: Add compatible string for JZ4770

Add a compatible string for the LCD controller found in the JZ4770 SoC.

v2: No change
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191210144142.33143-1-paul@crapouillou.net
# *** extracted tags ***
Acked-by: Sam Ravnborg <sam@ravnborg.org>

Documentation/devicetree/bindings/display/ingenic,lcd.txt

@@ -4,6 +4,7 @@ Required properties:
 - compatible: one of:
   * ingenic,jz4740-lcd
   * ingenic,jz4725b-lcd
+  * ingenic,jz4770-lcd
 - reg: LCD registers location and length
 - clocks: LCD pixclock and device clock specifiers.
 	   The device clock is only required on the JZ4740.