ASoC: cleanup duplicated code.

Many codec drivers were implementing cookie-cutter copies of the function
that adds kcontrols to the codec.

This patch moves this code to a common function snd_soc_add_controls() in
soc-core.c and updates all drivers using copies of this function to use the
new common version.

[Edited to raise priority of error log message and document parameters.
 -- broonie]

Signed-off-by: Ian Molton <ian@mnementh.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>