Add support for on-chip I2C controller used on old UniPhier SoCs
such as PH1-LD4, PH1-sLD8, etc.  This adapter is so simple that
it has no FIFO in it.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>