ALSA: ASoC: Add OpenFirmware helper for matching bus and codec drivers

Simple utility layer for creating ASoC machine instances based on data
in the OpenFirmware device tree.  OF aware platform drivers and codec
drivers register themselves with this framework and the framework
automatically instantiates a machine driver.  At the moment, the driver
is not very capable and it is expected to be extended as more features
are needed for specifying the configuration in the device tree.

This is most likely temporary glue code to work around limitations in
the ASoC v1 framework.  When v2 is merged, most of this driver will
need to be reworked.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
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>