ASoC: tas2764: Fix amp gain register offset & default

[ Upstream commit 1c4f29ec

 ]

The register default is 0x28 per the datasheet, and the amp gain field
is supposed to be shifted left by one. With the wrong default, the ALSA
controls lie about the power-up state. With the wrong shift, we get only
half the gain we expect.

Signed-off-by: Hector Martin <marcan@marcan.st>
Fixes: 827ed8a0

 ("ASoC: tas2764: Add the driver for the TAS2764")
Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20220630075135.2221-4-povik+lin@cutebit.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>