ASoC: tas2552: Fix off-by-one for max_register setting

The latest valid register is TAS2552_VBAT_DATA.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Dan <Murphy&lt;dmurphy@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>