ASoC: rl6231: avoid using divisible by 3 for DMIC clk

Few codecs will meet no DMIC clock output issue when select a divided
number which is divisible by 3. To prevent this issue, the patch ignore
the numbers when calculating the DMIC clock divider.

Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>