regmap: Use mas_walk() instead of mas_find()

Liam recommends using mas_walk() instead of mas_find() for our use case so
let's do that, it avoids some minor overhead associated with being able to
restart the operation which we don't need since we do a simple search.

Suggested-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230403-regmap-maple-walk-fine-v2-1-c07371c8a867@kernel.org


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