sysctl: remove __user qualifier from stack_erasing_sysctl buffer argument

The buffer arg in proc handler functions have been void* (no __user
qualifier) since commit 32927393dc ("sysctl: pass kernel pointers to
->proc_handler"). The __user qualifier was erroneously brought back in
commit 0df8bdd5e3 ("stackleak: move stack_erasing sysctl to
stackleak.c"). This fixes the error by removing the __user qualifier.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202510221719.3ggn070M-lkp@intel.com/
Signed-off-by: Joel Granados <joel.granados@kernel.org>

kernel/kstack_erase.c

@@ -23,7 +23,7 @@ static DEFINE_STATIC_KEY_FALSE(stack_erasing_bypass);
 
 #ifdef CONFIG_SYSCTL
 static int stack_erasing_sysctl(const struct ctl_table *table, int write,
-			void __user *buffer, size_t *lenp, loff_t *ppos)
+			void *buffer, size_t *lenp, loff_t *ppos)
 {
 	int ret = 0;
 	int state = !static_branch_unlikely(&stack_erasing_bypass);