Revert "android: binder: stop saving a pointer to the VMA"

This reverts commit 622ef885 which is
commit a43cfc87 upstream.

This breaks the GKI kernel ABI, and will need to be re-added in an
ABI-stable way if it is still needed in this kernel branch.

Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Carlos Llamas <cmllamas@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I698efd7b38ededaf4bb321821d0072b28b8e4c0c