sepolicy: Allow system server and uncrypt access pipe

System server needs to be able to create a pipe in the cache partition
for uncrypting OTAs. Uncrypt needs to be able to read and write the
pipe.

Change-Id: Ie03ee7d637eaecff8fe38bf03dc733b3915cd336
diff --git a/sepolicy/system_server.te b/sepolicy/system_server.te
index a9000b6..6aaf50c 100644
--- a/sepolicy/system_server.te
+++ b/sepolicy/system_server.te
@@ -1,5 +1,6 @@
 allow system_server recovery_cache_file:dir rw_dir_perms;
 allow system_server recovery_cache_file:file create_file_perms;
+allow system_server recovery_cache_file:fifo_file create_file_perms;
 
 # Persistent properties
 allow system_server persist_property_file:dir rw_dir_perms;