input: sensors: fix the power issues of akm09911

The power management of the driver is not correctly handled and may
cause failures under some condition. Fix the regualator configration
issues by adding more dedicated function to handle the power issue.

Change-Id: I65a47e79f6777b2c71a33fbc370c797d79b1992f
CRs-fixed: 639666
Signed-off-by: Oliver Wang <mengmeng@codeaurora.org>