KVM: Open code kvm_delete_memslot() into its only caller

Fold kvm_delete_memslot() into __kvm_set_memory_region() to free up the
"kvm_delete_memslot()" name for use in a future helper.  The delete logic
isn't so complex/long that it truly needs a helper, and it will be
simplified a wee bit further in upcoming commits.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Message-Id: <2887631c31a82947faa488ab72f55f8c68b7c194.1638817638.git.maciej.szmigiero@oracle.com>

virt/kvm/kvm_main.c

@@ -1668,29 +1668,6 @@ static int kvm_set_memslot(struct kvm *kvm,
 	return r;
 }
 
-static int kvm_delete_memslot(struct kvm *kvm,
-			      const struct kvm_userspace_memory_region *mem,
-			      struct kvm_memory_slot *old, int as_id)
-{
-	struct kvm_memory_slot new;
-
-	if (!old->npages)
-		return -EINVAL;
-
-	if (WARN_ON_ONCE(kvm->nr_memslot_pages < old->npages))
-		return -EIO;
-
-	memset(&new, 0, sizeof(new));
-	new.id = old->id;
-	/*
-	 * This is only for debugging purpose; it should never be referenced
-	 * for a removed memslot.
-	 */
-	new.as_id = as_id;
-
-	return kvm_set_memslot(kvm, mem, &new, as_id, KVM_MR_DELETE);
-}
-
 /*
  * Allocate some memory and give it an address in the guest physical address
  * space.
@@ -1747,8 +1724,23 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		old.id = id;
 	}
 
-	if (!mem->memory_size)
-		return kvm_delete_memslot(kvm, mem, &old, as_id);
+	if (!mem->memory_size) {
+		if (!old.npages)
+			return -EINVAL;
+
+		if (WARN_ON_ONCE(kvm->nr_memslot_pages < old.npages))
+			return -EIO;
+
+		memset(&new, 0, sizeof(new));
+		new.id = id;
+		/*
+		 * This is only for debugging purpose; it should never be
+		 * referenced for a removed memslot.
+		 */
+		new.as_id = as_id;
+
+		return kvm_set_memslot(kvm, mem, &new, as_id, KVM_MR_DELETE);
+	}
 
 	new.as_id = as_id;
 	new.id = id;