iio: core: Fix entry not deleted when iio_register_sw_trigger_type() fails

In iio_register_sw_trigger_type(), configfs_register_default_group() is
possible to fail, but the entry add to iio_trigger_types_list is not
deleted.

This leaves wild in iio_trigger_types_list, which can cause page fault
when module is loading again. So fix this by list_del(&t->list) in error
path.

BUG: unable to handle page fault for address: fffffbfff81d7400
Call Trace:
<TASK>
iio_register_sw_trigger_type
do_one_initcall
do_init_module
load_module
...

Fixes: b662f809d410 ("iio: core: Introduce IIO software triggers")
Signed-off-by: Chen Zhongjin <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Cc: <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/industrialio-sw-trigger.c

···
 
 	t->group = configfs_register_default_group(iio_triggers_group, t->name,
 						&iio_trigger_type_group_type);
-	if (IS_ERR(t->group))
+	if (IS_ERR(t->group)) {
+		mutex_lock(&iio_trigger_types_lock);
+		list_del(&t->list);
+		mutex_unlock(&iio_trigger_types_lock);
 		ret = PTR_ERR(t->group);
+	}
 
 	return ret;
 }