util: Make it possible to default construct pmr alloc
util: Make it possible to default construct pmr alloc

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