Add constant describing virtual device connections. am: 751926f0f2

Original change: https://android-review.googlesource.com/c/platform/system/hardware/interfaces/+/2393914

Change-Id: I138201dc98c095a922d81d34d74d00823ddb647e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>