trace: fix an incorrect __user annotation on stack_trace_sysctl

No user pointers for sysctls anymore.

Fixes: 32927393dc ("sysctl: pass kernel pointers to ->proc_handler")
Reported-by: build test robot <lkp@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

kernel/trace/trace_stack.c

@@ -515,9 +515,8 @@ static const struct file_operations stack_trace_filter_fops = {
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
 int
-stack_trace_sysctl(struct ctl_table *table, int write,
-		   void __user *buffer, size_t *lenp,
-		   loff_t *ppos)
+stack_trace_sysctl(struct ctl_table *table, int write, void *buffer,
+		   size_t *lenp, loff_t *ppos)
 {
 	int was_enabled;
 	int ret;