regulator: s2mps11: Use devm_regulator_register

Commit e398b51a ("regulator: s2mps11: Convert to devm_regulator_register()")
intended to do this conversion. However the actual conversion to devm_* got
missed out. Fix this.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>