Add OWNERS for MTP functionality am: b123928699

Original change: https://android-review.googlesource.com/c/platform/packages/services/Mtp/+/2628009

Change-Id: I733cc9c1a9305b1993f097a86b839972864429ee
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>