dt-bindings: display: panel: sitronix,st7701: Add Densitron DMT028VGHMCMI-1A TFT

Add compatible string for Densitron DMT028VGHMCMI-1A TFT matrix.
This is a DSI-attached 480x640 2.83 inch panel.

Signed-off-by: Marek Vasut <[e-mail]>
Cc: Guido Günther <[e-mail]>
Cc: Jagan Teki <[e-mail]>
Cc: Laurent Pinchart <[e-mail]>
Cc: Linus Walleij <[e-mail]>
Cc: Rob Herring <[e-mail]>
Cc: Sam Ravnborg <[e-mail]>
Cc: Thierry Reding <[e-mail]>
Cc: [e-mail]
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Documentation/devicetree/bindings/display/panel/sitronix,st7701.yaml

···
   Techstar TS8550B is 480x854, 2-lane MIPI DSI LCD panel which has
   inbuilt ST7701 chip.
 
+  Densitron DMT028VGHMCMI-1A is 480x640, 2-lane MIPI DSI LCD panel
+  which has built-in ST7701 chip.
+
 allOf:
   - $ref: panel-common.yaml#
 
···
   compatible:
     items:
       - enum:
+          - densitron,dmt028vghmcmi-1a
           - techstar,ts8550b
       - const: sitronix,st7701