Add ocontext for F2FS

Without this, the "seclabel" mount option is unavailable to F2FS.

Bug: 15388455
Change-Id: I8d141a0d4d14df9fe84d3b131484e9696fcd8870

fs_use

@@ -6,6 +6,7 @@ fs_use_xattr ext3 u:object_r:labeledfs:s0;
 fs_use_xattr ext4 u:object_r:labeledfs:s0;
 fs_use_xattr xfs u:object_r:labeledfs:s0;
 fs_use_xattr btrfs u:object_r:labeledfs:s0;
+fs_use_xattr f2fs u:object_r:labeledfs:s0;
 
 # Label inodes from task label.
 fs_use_task pipefs u:object_r:pipefs:s0;