UPSTREAM: selinux: enable genfscon labeling for tracefs

In kernel version 4.1, tracefs was separated from debugfs into its
own filesystem. Prior to this split, files in
/sys/kernel/debug/tracing could be labeled during filesystem
creation using genfscon or later from userspace using setxattr. This
change re-enables support for genfscon labeling.

Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
(cherry picked from commit 6a3911837da0a90ed599fd0a9836472f5e7ddf1b)
Change-Id: I98ad8c829302346705c1abcdc8f019f479fdefb6
Bug: 62413700