dt-bindings: rtc: merge ds1339 in ds1307 documentation

Now that there is documentation for the ds1307 and compatible RTCs, merge
the ds1339 documentation in it.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/rtc/dallas,ds1339.txt

-* Dallas DS1339		I2C Serial Real-Time Clock
-
-Required properties:
-- compatible: Should contain "dallas,ds1339".
-- reg: I2C address for chip
-
-Optional properties:
-- trickle-resistor-ohms : Selected resistor for trickle charger
-	Values usable for ds1339 are 250, 2000, 4000
-	Should be given if trickle charger should be enabled
-- trickle-diode-disable : Do not use internal trickle charger diode
-	Should be given if internal trickle charger diode should be disabled
-Example:
-	ds1339: rtc@68 {
-		compatible = "dallas,ds1339";
-		trickle-resistor-ohms = <250>;
-		reg = <0x68>;
-	};

Documentation/devicetree/bindings/rtc/rtc-ds1307.txt

@@ -26,6 +26,13 @@ Optional properties:
 - clock-output-names: From common clock binding to override the default output
                       clock name
 - wakeup-source: Enables wake up of host system on alarm
+- trickle-resistor-ohms : ds1339, ds1340 and ds 1388 only
+	Selected resistor for trickle charger
+	Possible values are 250, 2000, 4000
+	Should be given if trickle charger should be enabled
+- trickle-diode-disable : ds1339, ds1340 and ds 1388 only
+	Do not use internal trickle charger diode
+	Should be given if internal trickle charger diode should be disabled
 
 Example:
 	rtc1: ds1339@68 {
@@ -33,4 +40,5 @@ Example:
 		reg = <0x68>;
 		interrupt-parent = <&gpio4>;
 		interrupts = <20 0>;
+		trickle-resistor-ohms = <250>;
 	};