nilfs2: remove references to long gone super operations

->delete_inode(), ->write_super_lockfs(), ->unlockfs() are gone so remove
references to them in the NTFS code.  Noticed while cleaning up the
fsfreeze mess.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>