sepolicy: Allow hal_memtrack_default search access to sysfs_kgsl

Grant hal_memtrack_default search access to sysfs_kgsl. This fixes
these avc denials seen in user build:
memtrack@1.0-se: type=1400 audit(0.0:2817): avc: denied { search }
for name="kgsl" dev="sysfs" ino=36355
scontext=u:r:hal_memtrack_default:s0
tcontext=u:object_r:sysfs_kgsl:s0 tclass=dir permissive=0

GL and EGL memory are now accounted properly when
"dumpsys meminfo -a <pid>" is executed in user build.

Change-Id: I1601729d4051bc3447a6f680ff38f3aa031efbde