regulator: max8952: Use managed regulator registration

Use managed devm_regulator_register to simplify the driver probe and
driver remove functions. This allows removing from state container the
pointer to regulator_dev returned on registering the regulator.

Patch also removes from state container pointer to 'struct device' as it
is not used anywhere outside of max8952_pmic_probe() function.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>