Kernel: Add AnonymousVMObject constructor for a Vector of physical pages

This will be used later on by the AHCI code to create a Region
that spans over scattered DMA pages.

Kernel/VM/VMObject.cpp

@@ -35,6 +35,11 @@ VMObject::VMObject(const VMObject& other)
     MM.register_vmobject(*this);
 }
 
+VMObject::VMObject()
+{
+    MM.register_vmobject(*this);
+}
+
 VMObject::VMObject(size_t size)
 {
     m_physical_pages.resize(ceil_div(size, static_cast<size_t>(PAGE_SIZE)));