i2c: mv64xxx: Add Allwinner sun4i compatible

Add the compatible string for the Allwinner A10 i2c controller and the
associated register layout.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>