dt-bindings: add more chips in documentation for Mediatek SoC

Add MT8127 & MT8135 from Mediatek.
Signed-off-by: Joe.C <yingjoe.chen@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>

Documentation/devicetree/bindings/arm/mediatek.txt

-Mediatek MT6589 Platforms Device Tree Bindings
+MediaTek mt65xx & mt81xx Platforms Device Tree Bindings
 
-Boards with a SoC of the Mediatek MT6589 shall have the following property:
+Boards with a MediaTek mt65xx/mt81xx SoC shall have the following property:
 
 Required root node property:
 
-compatible: must contain "mediatek,mt6589"
+compatible: Must contain one of
+   "mediatek,mt6589"
+   "mediatek,mt8127"
+   "mediatek,mt8135"
 
 
 Supported boards:
@@ -12,3 +15,9 @@ Supported boards:
 - bq Aquaris5 smart phone:
     Required root node properties:
       - compatible = "mundoreader,bq-aquaris5", "mediatek,mt6589";
+- MTK mt8127 tablet moose EVB:
+    Required root node properties:
+      - compatible = "mediatek,mt8127-moose", "mediatek,mt8127";
+- MTK mt8135 tablet EVB:
+    Required root node properties:
+      - compatible = "mediatek,mt8135-evbp1", "mediatek,mt8135";