file_contexts

This change helps with the following denials.
  avc:  denied  { write } for  pid=14157 comm="Thread-88" name="premium_sms_policy.xml" dev="mmcblk0p28" ino=618998 scontext=u:r:radio:s0 tcontext=u:object_r:system_data_file:s0 tclass=file
  avc:  denied  { write } for  pid=14293 comm="Thread-89" name="sms" dev="mmcblk0p28" ino=618952 scontext=u:r:radio:s0 tcontext=u:object_r:system_data_file:s0 tclass=dir

Prior to this patch the directory was labeled as
system_data_file which is a bit too generic. This
directory contains xml files with regexs which
represent premium numbers that are used to warn
the user before sending.

Change-Id: I98288b25aa1546477e05eee9f7622324b013e695
Signed-off-by: rpcraig <rpcraig@tycho.ncsc.mil>