f2fs: spread f2fs_set_inode_flags()

This patch changes codes as below:
- use f2fs_set_inode_flags() to update i_flags atomically to avoid
potential race.
- synchronize F2FS_I(inode)->i_flags to inode->i_flags in
f2fs_new_inode().
- use f2fs_set_inode_flags() to simply codes in f2fs_quota_{on,off}.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -3422,7 +3422,7 @@ static inline void f2fs_set_encrypted_inode(struct inode *inode)
 {
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 	file_set_encrypt(inode);
-	inode->i_flags |= S_ENCRYPTED;
+	f2fs_set_inode_flags(inode);
 #endif
 }