dt-bindings: Add DT bindings for Powertip PH800480T013

Add DT bindings for Powertip PH800480T013 800x480 parallel LCD,
this one is used in the Raspberry Pi 7" touchscreen display unit.
Signed-off-by: Marek Vasut <marex@denx.de>
To: dri-devel@lists.freedesktop.org
Cc: Eric Anholt <eric@anholt.net>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200728121246.23304-2-marex@denx.de

Documentation/devicetree/bindings/display/panel/panel-simple.yaml

@@ -219,6 +219,8 @@ properties:
       - osddisplays,osd070t1718-19ts
         # One Stop Displays OSD101T2045-53TS 10.1" 1920x1200 panel
       - osddisplays,osd101t2045-53ts
+        # POWERTIP PH800480T013-IDF2 7.0" WVGA TFT LCD panel
+      - powertip,ph800480t013-idf02
         # QiaoDian XianShi Corporation 4"3 TFT LCD panel
       - qiaodian,qd43003c0-40
         # Rocktech Displays Ltd. RK101II01D-CT 10.1" TFT 1280x800