regmap: sdw: Update misleading comment

In the regmap config reg_bits represents the number of address bits not
the number of value bits. Correct the misleading comment which looks a
lot like it suggests the register value itself is 32-bits wide.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230112171840.2098463-2-ckeepax@opensource.cirrus.com


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