linux-wandboard

vgaarbiter: fix a typo in the vgaarbiter Documentation

I detected a typo, while reading "Documentation/vgaarbiter.txt".  Fix the
'fieldd' mispelling.

Signed-off-by: Detlef Riekenberg <wine.dev@web.de>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>