misc: remove ineffective WARN_ON() check from misc_deregister()

The WARN_ON(list_empty(&misc->list)) in misc_deregister() does
not catch any practical error conditions:
- For statically allocated miscdevice structures, the list pointers
 are zero-initialized, so list_empty() returns false, not true.
- After list_del(), the pointers are set to LIST_POISON1 and LIST_POISON2,
 so repeated deregistration also fails to trigger the check.

Signed-off-by: Xion Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Xion Wang

drivers/char/misc.c

@@ -283,9 +283,6 @@ EXPORT_SYMBOL(misc_register);
 
 void misc_deregister(struct miscdevice *misc)
 {
-	if (WARN_ON(list_empty(&misc->list)))
-		return;
-
 	mutex_lock(&misc_mtx);
 	list_del(&misc->list);
 	device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));