firmware: Do not use WARN_ON(!spin_is_locked())

spin_is_locked() always returns false for uniprocessor configurations
in several architectures, so do not use WARN_ON with it.
Use lockdep_assert_held() instead to also reduce overhead in
non-debug kernels.

Signed-off-by: Guenter Roeck <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Matt Fleming <[e-mail]>

drivers/firmware/efi/vars.c

···
  */
 static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
 {
-	WARN_ON(!spin_is_locked(&__efivars->lock));
+	lockdep_assert_held(&__efivars->lock);
 
 	list_del(&entry->list);
 	spin_unlock_irq(&__efivars->lock);
···
 	const struct efivar_operations *ops = __efivars->ops;
 	efi_status_t status;
 
-	WARN_ON(!spin_is_locked(&__efivars->lock));
+	lockdep_assert_held(&__efivars->lock);
 
 	status = ops->set_variable(entry->var.VariableName,
 				   &entry->var.VendorGuid,
···
 	int strsize1, strsize2;
 	bool found = false;
 
-	WARN_ON(!spin_is_locked(&__efivars->lock));
+	lockdep_assert_held(&__efivars->lock);
 
 	list_for_each_entry_safe(entry, n, head, list) {
 		strsize1 = ucs2_strsize(name, 1024);
···
 	const struct efivar_operations *ops = __efivars->ops;
 	efi_status_t status;
 
-	WARN_ON(!spin_is_locked(&__efivars->lock));
+	lockdep_assert_held(&__efivars->lock);
 
 	status = ops->get_variable(entry->var.VariableName,
 				   &entry->var.VendorGuid,