ASoC: rt5631: Fixing compilation warning when DT is disabled

Fixes the following compilation warning:
Warning: 'rt5631_i2c_dt_ids' defined but not used - when DT is not used.

Signed-off-by: Claude Youn <claude.youn@gmail.com>
Signed-off-by: Krishna Mohan Dani <krishna.md@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>