regulator: rtq2208: Fix the LDO DVS capability

Use the hidden bank register to identify whether the LDO voltage is
fixed or variable. Remove the read of 'richtek,fixed-microvolt'
property.

Fixes: af1296d1 ("regulator: rtq2208: Add fixed LDO VOUT property and check that matches the constraints")
Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Link: https://patch.msgid.link/dae0321b710518ce32260336e3cc9caf2ba84215.1742204502.git.cy_huang@richtek.com


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