ASoC: qcom: lpass-ipq806x: fix bitwidth regmap field

BIT_WIDTH field in I2S_CTL register is two bits wide, however
recent regmap field conversion patch trimmed it down to one bit.
Fix this by correcting the bit range!

Fixes: b5022a36

 ("ASoC: qcom: lpass: Use regmap_field for i2sctl and dmactl registers")
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20210119174700.32639-1-srinivas.kandagatla@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>