ASoC: tas2764: Allow mono streams

ASoC: tas2764: Allow mono streams

The part is a mono speaker amp, but it can do downmix and switch between
left and right channel, so the right channel range is 1 to 2.

(This mirrors commit bf54d97a835d ("ASoC: tas2770: Allow mono streams")
which was a fix to the tas2770 driver.)

Fixes: 827ed8a0fa50 ("ASoC: tas2764: Add the driver for the TAS2764")
Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20220825140241.53963-2-povik+lin@cutebit.org
Signed-off-by: Mark Brown <broonie@kernel.org>