Doc: mfd: as3722: Add details of optional missing property

Add details of following properties which are used on driver but
not documented on DT binding document.
- ams,enable-internal-int-pullup
- ams,enable-internal-i2c-pullup

Reported-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/as3722.txt

@@ -13,6 +13,14 @@ Required properties:
   The second cell is the flags, encoded as the trigger masks from binding document
 	interrupts.txt, using dt-bindings/irq.
 
+Optional properties:
+--------------------
+- ams,enable-internal-int-pullup: Boolean property, to enable internal pullup on
+	interrupt pin. Missing this will disable internal pullup on INT pin.
+- ams,enable-internal-i2c-pullup: Boolean property, to enable internal pullup on
+	i2c scl/sda pins. Missing this will disable internal pullup on i2c
+	scl/sda lines.
+
 Optional submodule and their properties:
 =======================================