net_test: add support/documentation for vsyscall=xonly for 5.2+ host
am: 58a8141525

Change-Id: Ieae7e51ad59fbda243624154556d96711244f9a0
tree: dbf9fa3d8862fb3067093a1b94b9757013c87ee3
  1. devicetree/
  2. net/
  3. Android.bp