KVM: set_memory_region: Refactor commit_memory_region()

This patch makes the parameter old a const pointer to the old memory
slot and adds a new parameter named change to know the change being
requested: the former is for removing extra copying and the latter is
for cleaning up the code.

Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

virt/kvm/kvm_main.c

@@ -896,7 +896,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 
 	old_memslots = install_new_memslots(kvm, slots, &new);
 
-	kvm_arch_commit_memory_region(kvm, mem, old);
+	kvm_arch_commit_memory_region(kvm, mem, &old, change);
 
 	kvm_free_physmem_slot(&old, &new);
 	kfree(old_memslots);