ARM: mediatek: dts: Cleanup bindings documentation

This patch cleans up the binding documentation stating explicitly
the binding and it's fallback for every SoC.
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/watchdog/mtk-wdt.txt

@@ -3,9 +3,8 @@ Mediatek SoCs Watchdog timer
 Required properties:
 
 - compatible should contain:
-	* "mediatek,mt2701-wdt" for MT2701 compatible watchdog timers
-	* "mediatek,mt6589-wdt" for all compatible watchdog timers (MT2701,
-		MT6589)
+	"mediatek,mt2701-wdt", "mediatek,mt6589-wdt": for MT2701
+	"mediatek,mt6589-wdt": for MT6589
 
 - reg : Specifies base physical address and size of the registers.