f2fs: support project quota

This patch adds to support plain project quota.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index 273ccb2..b8f495a 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -164,6 +164,7 @@
                        with "mode=lfs".
 usrquota               Enable plain user disk quota accounting.
 grpquota               Enable plain group disk quota accounting.
+prjquota               Enable plain project quota accounting.
 
 ================================================================================
 DEBUGFS ENTRIES