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-pnx.txt

@@ -0,0 +1,36 @@
+* NXP PNX I2C Controller
+
+Required properties:
+
+ - reg: Offset and length of the register set for the device
+ - compatible: should be "nxp,pnx-i2c"
+ - interrupts: configure one interrupt line
+ - #address-cells: always 1 (for i2c addresses)
+ - #size-cells: always 0
+ - interrupt-parent: the phandle for the interrupt controller that
+   services interrupts for this device.
+
+Optional properties:
+
+ - clock-frequency: desired I2C bus clock frequency in Hz, Default: 100000 Hz
+
+Examples:
+
+	i2c1: i2c@400a0000 {
+		compatible = "nxp,pnx-i2c";
+		reg = <0x400a0000 0x100>;
+		interrupt-parent = <&mic>;
+		interrupts = <51 0>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};
+
+	i2c2: i2c@400a8000 {
+		compatible = "nxp,pnx-i2c";
+		reg = <0x400a8000 0x100>;
+		interrupt-parent = <&mic>;
+		interrupts = <50 0>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		clock-frequency = <100000>;
+	};