Char: vt_ioctl, fix BKL imbalance

Stanse found (again) a BKL imbalance in vt_ioctl.

It's easily triggerable by ioctl(dev_tty_fd, VT_SETACTIVATE, NULL);

Introduced by

commit d3b5cffc                                 Author: Alan Cox <alan@linux.intel.com>
Date:   Sat Sep 19 13:13:26 2009 -0700

    vt: add an activate and lock

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>