regulator: max8952: Separate constraints from platform data struct

This patch modifies platform data structure of max8952 driver to
use pointer to regulator_init_data struct instead of embedding it.

This is a prerequisite for adding Device Tree support for the driver.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>