system_server: search permission to all of sysfs.

This will allow system_server to perfom path resolution on paths like:
/sys/devices/soc/800f000.qcom,spmi/spmi-0/spmi0-00/800f000.qcom,spmi:qcom,pm8998@0:qcom,pm8998_rtc/rtc

Fixes this denial:
avc: denied { search } for pid=947 comm=system_server
name=800f000.qcom,spmi dev=sysfs ino=19891
scontext=u:r:system_server:s0 tcontext=u:object_r:sysfs_msm_subsys:s0
tclass=dir permissive=0 b/68003344

Bug: 68003344
Test: walleye boots without the denial above.
Change-Id: Ib282395124c7f2f554681fcc713b9afe189f441c