Impact: add new API for drivers

Add implementation of readq/writeq to x86_32, and add config value to
the x86 architecture to determine existence of readq/writeq.
Signed-off-by: NHitoshi Mitake <h.mitake@gmail.com>
Acked-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>