vgaarb: Fix a few checkpatch errors and warnings

Wrap overly long lines (offending lines were mostly comments, so trivial
to fix up) and a number of other coding style issues pointed out by the
checkpatch tool.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>