power_supply: Use max8925 platform_data from cell

Avoid to get platform_data from parent device. Get it from mfd cell
device instead.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Acked-by: Anton Vorontsov <cbou@mail.ru>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>