vt: use msecs_to_jiffies for time conversion

Converting milliseconds to jiffies by "val * HZ / 1000" is technically
OK but msecs_to_jiffies(val) is the cleaner solution and handles all
corner cases correctly. This is a minor API consolidation only and
should make things more readable.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>