Add __INTRODUCED_IN to more NdkMediaFormat.h variables

Annotate the ones that were added when the NDK media APIs were first
added in API 21

Test: build
Bug: 113052379
Change-Id: Id60039944981f3af56571f2de31e7989e4d377a2
Merged-In: Id60039944981f3af56571f2de31e7989e4d377a2
(cherry picked from commit e2d5f7bc3b45a2dc3e072f02d6efdcc767e49c4e)
2 files changed