Allow all domains to stat symlinks in sysfs

This is needed to retain app's previous access to
/sys/devices/system/cpu. When these files were previously
labeled in file_contexts, symlinks were labeled as
sysfs_devices_system_cpu. When labeling was moved to genfs_contexts
symlinks all have the default sysfs label.

avc: denied { getattr } for comm="main"
path="/sys/devices/system/cpu/cpu0/cpufreq" dev="sysfs" ino=41897
scontext=u:r:untrusted_app_25:s0:c512,c768
tcontext=u:object_r:sysfs:s0 tclass=lnk_file permissive=0

Change-Id: Idaa565390bca13d3819e147fcea4214956c0f589
Bug: 64270911
Test: build aosp_marlin
(cherry picked from commit 8d021a94)