i2c: mv64xxx: Add I2C Transaction Generator support

The I2C Transaction Generator offloads CPU from managing I2C
transfer step by step.

This feature is currently only available on Armada XP, so usage of
this mechanism is activated through device tree.

Based on the work of Piotr Ziecik and rewrote to use the new way of
handling multiples i2c messages.
Signed-off-by: Piotr Ziecik <kosmo@semihalf.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt

@@ -5,6 +5,7 @@ Required properties :
 
  - reg             : Offset and length of the register set for the device
  - compatible      : Should be "marvell,mv64xxx-i2c" or "allwinner,sun4i-i2c"
+                     or "marvell,mv7230-i2c"
  - interrupts      : The interrupt number
 
 Optional properties :
@@ -20,3 +21,12 @@ Examples:
 		interrupts = <29>;
 		clock-frequency = <100000>;
 	};
+
+For the Armada XP:
+
+	i2c@11000 {
+		compatible = "marvell,mv78230-i2c", "marvell,mv64xxx-i2c";
+		reg = <0x11000 0x100>;
+		interrupts = <29>;
+		clock-frequency = <100000>;
+	};