ASoC: ak4641: 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. This driver was merged after the change of DAIs are
matched was made and the IDs were never used and presumably never will be,
so remove them.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>