Fix ImeSubtypeListItem ordering

The previous CL (I47f902cc8f) fixed ImeSubtypeListItem.compareTo() is
compliant to Comparable#compareTo(T) (Bug 34255739) and introduced the
following order of comparing ImeSubtypeListItem fields.

  1. ImeSubtypeListItem#mImeName
  2. ImeSubtypeListItem#mSubtypeName
  3. ImeSubtypeListItem#mIsSystemLocale
  4. ImeSubtypeListItem#mIsSystemLanguage

But it didn't keep the previous ordering (Bug 34821121).  This CL
fixes the order of comparing ImeSubtypeListItem fields as compatible
as ones before I47f902cc8f.

  1. ImeSubtypeListItem#mImeName
  2. ImeSubtypeListItem#mIsSystemLocale
  3. ImeSubtypeListItem#mIsSystemLanguage
  4. ImeSubtypeListItem#mSubtypeName

Bug: 34255739
Fixes: 34821121
Test: Install FramewroksCoreTests.apk and run
      InputMethodSubtypeSwitchingControllerTest and verify all tests passed.
Change-Id: I813403fd29c5c52a3ca375174ec4b95e4b5433f2