tty: vt: fix up tabstops properly

Tabs on a console with long lines do not wrap properly, so correctly
account for the line length when computing the tab placement location.

Reported-by: James Holderness <j4_james@hotmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>