vt(4) chops off the leftmost three columns

[Alan Somers]

I've seen three separate machines where FreeBSD11's vt(4) driver chops
off the leftmost three columns of the screen.  Rendering simply starts
at the beginning of the fourth column.  In all cases, setting
"kern.vty=sc" corrects the problem.  The three different systems are:

1) Haswell CPU with SuperMicro X10DRH-IT motherboard
2) Gainestown CPU with Dell S99 motherboard
3) Via Nano X2 CPU with VIA EPIA-M900 motherboard

I don't have time to hack on vt myself as long as sc works fine.  But
if there's any way that I can help a vt developer, I'd be happy to do
it.

-Alan