power: smb1390-psy: Optimize power_supply_changed call flow

Currently, power_supply_changed is call on every run through cp
disable votable callback function. Optimize this, to call power_
supply_changed only in case of a change in its disable status.

Change-Id: Ic95e5c6e59d59988a0c2b592f15987e2f24716a9
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>