ALSA: ASoC: Add AK4535 driver

The AK4535 codec is included in some HP iPAQ systems.

This driver was originally written by Richard Purdie and with some bug
fixes from Milan Plzik.  While out of tree it has also had some
mechanical updates for new APIs and current best practices from Liam
Girdwood, Graeme Gregory and Mark Brown.

Signed-off-by: Richard Purdie <richard@openedhand.com>
Signed-off-by: Milan Plzik <milan.plzik@gmail.com>
Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Signed-off-by: Graeme Gregory <gg@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>