Move sysfs_devices_system_cpu to the central policy.

Every device has a CPU. This is not device specific.

Allow every domain to read these files/directories.
For unknown reasons, these files are accessed by A LOT
of processes.

Allow ueventd to write to these files. This addresses
the following denials seen on mako:

<5>[    4.935602] type=1400 audit(1383167737.512:4): avc:  denied  { read } for  pid=140 comm="ueventd" name="cpu0" dev="sysfs" ino=3163 scontext=u:r:ueventd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=dir
<5>[    4.935785] type=1400 audit(1383167737.512:5): avc:  denied  { open } for  pid=140 comm="ueventd" name="cpu0" dev="sysfs" ino=3163 scontext=u:r:ueventd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=dir
<5>[    4.935937] type=1400 audit(1383167737.512:6): avc:  denied  { search } for  pid=140 comm="ueventd" name="cpu0" dev="sysfs" ino=3163 scontext=u:r:ueventd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=dir
<5>[    4.936120] type=1400 audit(1383167737.512:7): avc:  denied  { write } for  pid=140 comm="ueventd" name="uevent" dev="sysfs" ino=3164 scontext=u:r:ueventd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file
<5>[    4.936303] type=1400 audit(1383167737.512:8): avc:  denied  { open } for  pid=140 comm="ueventd" name="uevent" dev="sysfs" ino=3164 scontext=u:r:ueventd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file

Change-Id: I4766dc571762d8fae06aa8c26828c070b80f5936