dt/bindings: Add bindings for Micro Crystal rv8803

... and Epson RX8900 real time clock

Signed-off-by: Oleksij Rempel <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>

Documentation/devicetree/bindings/rtc/epson,rx8900.txt

···
+Real Time Clock driver for:
+  - Epson RX8900
+  - Micro Crystal rv8803
+
+Required properties:
+- compatible: should be: "microcrystal,rv8803" or "epson,rx8900"
+- reg : the I2C address of the device for I2C
+
+Optional properties:
+- epson,vdet-disable : boolean, if present will disable voltage detector.
+  Should be set if no backup battery is used.
+- trickle-diode-disable : boolean, if present will disable internal trickle
+  charger diode
+
+Example:
+
+	rtc: rtc@32 {
+		compatible = "epson,rx8900"
+		reg = <0x32>;
+		epson,vdet-disable;
+		trickle-diode-disable;
+	};