SerializeFlags: remove legacyValue() API

Remove constructor with legacyValue (which contains NOT bits) and
getter to legacyValue. Instead, SerializeFlags objects are constructed
with positive flags.

Bug: 110711640
Test: libvintf_test
Change-Id: I41e2b913822b9e75b17a1f2336e5a35236e9671e
2 files changed