dt-bindings: watchdog: add Allwinner H6 watchdog

Allwinner H6 has a similar watchdog as the A64 which is already
a compatible of the A31.

This commit add the H6 compatible.
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

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

@@ -6,6 +6,7 @@ Required properties:
 	"allwinner,sun4i-a10-wdt"
 	"allwinner,sun6i-a31-wdt"
 	"allwinner,sun50i-a64-wdt","allwinner,sun6i-a31-wdt"
+	"allwinner,sun50i-h6-wdt","allwinner,sun6i-a31-wdt"
 	"allwinner,suniv-f1c100s-wdt", "allwinner,sun4i-a10-wdt"
 - reg : Specifies base physical address and size of the registers.