If the bitwidth passed in to the set_bitwidth function is not supported
then return an error.

Fixes: 29b74236bd57 ("ASoC: tas2562: Introduce the TAS2562 amplifier")
Signed-off-by: Dan Murphy <dmurphy@ti.com>
Link: https://lore.kernel.org/r/20200218185252.26290-1-dmurphy@ti.comSigned-off-by: Mark Brown <broonie@kernel.org>