regulator: max8997: remove dependency on platform_data pointer

The platform_data (pdata) may be pointing to __initdata section, which
may be free'd from the memory. The dependency on pdata in non-init
functions is removed in this patch to allow platform to declare
__initdata for platform data.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>