tty vt: Fix a regression in command line edition

tty vt: Fix a regression in command line edition

The commit 0ca3f324181581032e9721b1b9e096b1d4cef4a5
("Fix line garbage in virtual console on command line edition")
made a regression with some machines: some characters were not erased
after line edition.

This patch adjusts the number of moved characters and the size of the
region to be updated.

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Tested-by: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>