Restore sysfs_devices_system_cpu to domain.te

Lots of processes access CPU information. This seems to be triggered
by libraries loaded into every Android process. Allow the access.

Addresses the following denials:

adbd    : type=1400 audit(0.0:3): avc: denied { search } for name="cpu" dev="sysfs" ino=32 scontext=u:r:adbd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=dir permissive=1
adbd    : type=1400 audit(0.0:4): avc: denied { read } for name="online" dev="sysfs" ino=34 scontext=u:r:adbd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=1
adbd    : type=1400 audit(0.0:5): avc: denied { open } for path="/sys/devices/system/cpu/online" dev="sysfs" ino=34 scontext=u:r:adbd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=1
adbd    : type=1400 audit(0.0:6): avc: denied { getattr } for path="/sys/devices/system/cpu/online" dev="sysfs" ino=34 scontext=u:r:adbd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=1

Change-Id: Ie7bfae53bdf670028db724d2720447ead42bad35