regulator: da9052: Use lowercase regulator names to match the DT

Since c32569e3 ("regulator: Use of_node_name_eq for node name
comparisons"), regulator node name comparisons are case sensitive.
The DA9052 driver uses uppercase, but the DT has lowercase.

Fix this by using a lowercase regulator name to match the DT node name.

Fixes: c32569e3 ("regulator: Use of_node_name_eq for node name comparisons")
Cc: Support Opensource <support.opensource@diasemi.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>