x86, setup: Store the boot cursor state

Add a field to store the boot cursor state and implement this for VGA on
x86. This can then be used to set the default policy for the boot console.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
LKML-Reference: <1258142222-16092-1-git-send-email-mjg@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>