Move reading time field to inside HistoryItem.readFromParcel().

Also HistoryItem does not need to implement Parcelable interface,
just like other batterystats classes, readFromParcel() and
writeToParcel() are pair of symmetric methods, but those classes do
not implement Parcelable interface because readFromParcel() is not a
method of readFromParcel() interface.

Change-Id: I5ac974c9903c5639a6bb52fc0a53367f92187af0
Fix: 135442392
Test: reboot device and "adb shell dumpsys batterystats"