p1: drivers: power: bring back pmic regs updating process

it reverts partially: f84de6cf078276a8f71006f89e1c94b596313095

definitely it is not a good choice to write i2c directly.
the device was very slow after some time of use.

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: I86575c48ca5114926ec4c0383d80d630ae486914