FROMLIST: security: selinux: allow per-file labelling for binderfs

This patch allows genfscon per-file labeling for binderfs.
This is required to have separate permissions to allow
access to binder, hwbinder and vndbinder devices which are
relocating to binderfs.

Acked-by: Jeff Vander Stoep <jeffv@google.com>
Acked-by: Mark Salyzyn <salyzyn@android.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Hridya Valsaraju <hridya@google.com>

Bug: 136497735
(cherry picked from commit 7a4b51947475a7f67e2bd06c4a4c768e2e64a975
git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git
master)
Link: https://lore.kernel.org/patchwork/patch/1175776/
Change-Id: I105cc54b30ddd4120dc23a363bddc2f9d00e4dc4