ASoC: tas2770: Add missing bias level power states

Add the BIAS_STANDBY and BIAS_PREPARE to the set_bias_level or else the
driver will return -EINVAL which is not correct as they are valid
states.

Fixes: 1a476abc ("tas2770: add tas2770 smart PA kernel driver")
Signed-off-by: Dan Murphy <dmurphy@ti.com>
Link: https://lore.kernel.org/r/20200918190548.12598-2-dmurphy@ti.com


Signed-off-by: Mark Brown <broonie@kernel.org>