Make apex_available of nn hidl interfaces explicit in Android.bp

These are available to com.android.neuralnetworks via the baseline
apexAvailable map in build/soong/apex/apex.go. This CL makes this
explicit in Android.bp

Test: m nothing #passes
Bug: 281077552
Change-Id: I9f08db0dba6b155c6f25393a5d4baf6de27110da
4 files changed