SELinux: Allow hostapd to read wifi data files under /persist.

Addresses the following denials:
  avc:  denied  { search } for  pid=9143 comm="hostapd" name="wifi" dev="mmcblk0p16" ino=12 scontext=u:r:hostapd:s0 tcontext=u:object_r:persist_wifi_file:s0 tclass=dir
  avc:  denied  { getattr } for  pid=9143 comm="hostapd" path="/persist/wifi/.macaddr" dev="mmcblk0p16" ino=19 scontext=u:r:hostapd:s0 tcontext=u:object_r:persist_wifi_file:s0 tclass=file
  avc:  denied  { read } for  pid=9143 comm="hostapd" name=".macaddr" dev="mmcblk0p16" ino=19 scontext=u:r:hostapd:s0 tcontext=u:object_r:persist_wifi_file:s0 tclass=file
  avc:  denied  { open } for  pid=9143 comm="hostapd" name=".macaddr" dev="mmcblk0p16" ino=19 scontext=u:r:hostapd:s0 tcontext=u:object_r:persist_wifi_file:s0 tclass=file

Change-Id: I5d84b3eb7a7d1dada1fa74f111aa6140acb921b6
Signed-off-by: rpcraig <rpcraig@tycho.ncsc.mil>