vt: hold console_sem across sysfs operations

Hold console sem while creating/destroying sysfs files.  Serialisation is
so far done by BKL held in tty release_dev and chrdev_open, but no other
locks are held in open path.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Aristeu Rozanski <aris@ruivo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>