ASoC: wm9712: Remove unused DAI ID defines

The DAI ID defines are back from the time when DAIs were referenced by a
numerical ID. These days a string is used for matching instead and the
defines are unused. The last user of these defines was removed in commit
f0fba2ad1b6b ("ASoC: multi-component - ASoC Multi-Component Support"). So
remove the defines as well.

This also means the wm9712.h file no longer has any content and can be
removed.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>