ASoC: pcm5102a: Add support for PCM5102A codec

Some definitions to support the PCM5102A codec
by Texas Instruments.

Signed-off-by: Florian Meier <florian.meier@koalo.de>

Changes to original patch by Florian Meier:
* rebased (Makefile and Kconfig
* fixed checkpath errors (spaces, newlines)
* added dt-binding documentation

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>