regmap: Fix double unlock in the maple cache

Doing the dance to drop the maple tree's internal spinlock means we need
multiple exit paths in our error handling.

Reported-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-unlock-v1-1-89998991b16c@kernel.org


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