Send BATTERY_CHANGED if maxChargingCurrent changes

Fixes a bug where the charging current on Keyguard was stale
on devices that don't immediately set the charging current.

Follow-up to I2e5c21dd7ec028ce47fb03ab71e74f7fccaa9e36

Bug: 8099739
Change-Id: I4b5b3b1231b1372310206941386dba743d5f88f4
3 files changed