google_battery: change the disconnect condition

A device is really disconnected (and google_battery needs to
generate the charging statistics) only when it see buck_en=0
in the charging flags and when charging state is DISCONNECTED
or UNKNOWN.

Bug: 203005295
Signed-off-by: AleX Pelosi <[email protected]>
Change-Id: I73c07f11a74a15f5d60730d624fd4e7866cedbe5
1 file changed