hw: Add flush_all() to devices
hw: Add flush_all() to devices

mnordsletten/IncludeOS,mnordsletten/IncludeOS,alfred-bratterud/IncludeOS,AnnikaH/IncludeOS,AndreasAakesson/IncludeOS,ingve/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,mnordsletten/IncludeOS,hioa-cs/IncludeOS,ingve/IncludeOS,ingve/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,mnordsletten/IncludeOS,mnordsletten/IncludeOS,ingve/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,alfred-bratterud/IncludeOS,mnordsletten/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,alfred-bratterud/IncludeOS,alfred-bratterud/IncludeOS,AndreasAakesson/IncludeOS,alfred-bratterud/IncludeOS,ingve/IncludeOS,AnnikaH/IncludeOS