[PATCH] oops-tracing: mention extended VGA

Something I've found handy countless times when users do this..

Signed-off-by: Dave Jones <davej@redhat.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>