dt-bindings: i2c: pxa: Update the documentation for the Armada 3700

This commit documents the compatible string to have the compatibility for
the I2C unit found in the Armada 3700.
Signed-off-by: Romain Perier <romain.perier@free-electrons.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

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

@@ -7,6 +7,7 @@ Required properties :
    compatible processor, e.g. pxa168, pxa910, mmp2, mmp3.
    For the pxa2xx/pxa3xx, an additional node "mrvl,pxa-i2c" is required
    as shown in the example below.
+   For the Armada 3700, the compatible should be "marvell,armada-3700-i2c".
 
 Recommended properties :