ARM: pxa: spitz: register spitz-audio device

Register spitz-audio device to be used by ASoC driver to bind ASoC
platform driver. Currently old 'soc-audio' approach is used, which needs
to be replaced with proper device.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>