pxa/hx4700: add platform device and I2C info for AK4641 codec

The audio on hx4700 needs this to properly work.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Dmitry Artamonow <mad_soft@inbox.ru>
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Tested-by: Paul Parsons <lost.distance@yahoo.com>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>