sound: ASoC: Convert neo1973/lm4857 to a new-style i2c driver

Convert the lm4857 driver in neo1973_wm8753 to the new (standard)
i2c device driver binding model. I assumed that the LM4857 was always
on the same I2C bus as the WM8753 codec.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Tim Niemeyer <reddog@mastersword.de>
Cc: Graeme Gregory <graeme@openmoko.org>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>