sepolicy: addressing memtracker debugfs access denials.

As debugfs is now restricted and any path need access has
to have a new label and rule to access.
hal_memtracker was using the /sys/kernel/debug/kgsl/
we are adding the  qti_debugfs secontext to this .

Denial:
memtrack@1.0-se: type=1400 audit(0.0:116): avc: denied { read } for name="mem"
dev="debugfs" ino=19172 scontext=u:r:hal_memtrack_default:s0
tcontext=u:object_r:debugfs:s0 tclass=file permissive=0

Change-Id: I2a08ff763db8f75168d079caa14cb6d1231e5df3