Document the AST2600 I2C bus compatible string.
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>