bindings: i2c: use consistent naming for i2c binding descriptions

Filenames of devictree binding documentation seems to be arbitrary and
for me it is unneeded hazzle to find the corresponding documentation for
a specific driver.

Naming the description the same as the driver is a lot easier and makes
sense to me since the driver defines the binding it understands.

Also, remove a reference in one source to the binding documentation, since path
information easily gets stale.

Signed-off-by: Wolfram Sang <wolfram@the-dreams.de>
Cc: Rob Herring <robherring2@gmail.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

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

@@ -0,0 +1,22 @@
+Xilinx IIC controller:
+
+Required properties:
+- compatible : Must be "xlnx,xps-iic-2.00.a"
+- reg : IIC register location and length
+- interrupts : IIC controller unterrupt
+- #address-cells = <1>
+- #size-cells = <0>
+
+Optional properties:
+- Child nodes conforming to i2c bus binding
+
+Example:
+
+	axi_iic_0: i2c@40800000 {
+		compatible = "xlnx,xps-iic-2.00.a";
+		interrupts = < 1 2 >;
+		reg = < 0x40800000 0x10000 >;
+
+		#size-cells = <0>;
+		#address-cells = <1>;
+	};