ntfs: remove references to long gone super operations and unimplemented methods

->delete_inode(), ->write_super_lockfs(), ->unlockfs() are gone so remove
refereces to them in the NTFS code.  Remove unnecessary comments about
unimplemented methods while at it (suggested by Christoph Hellwig).

Noticed while cleaning up the fsfreeze mess.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Cc: Anton Altaparmakov <anton@tuxera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>