media/ndk: add missing <functional> includes

Bug: 175635923
Test: m MODULES-IN-frameworks-av-media-ndk
Change-Id: I5e6f973da1bf784eefe24ebd54c263c2b12702ac
Merged-In: I5e6f973da1bf784eefe24ebd54c263c2b12702ac
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:dfbae85ab0fc83eba302f4eefb4cc6bd912538d5)
2 files changed