sched: remove _do_fork()

Now that all callers of _do_fork() have been switched to kernel_clone() remove
the _do_fork() helper.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20200819104655.436656-12-christian.brauner@ubuntu.com

include/linux/sched/task.h

@@ -84,10 +84,6 @@ extern void exit_files(struct task_struct *);
 extern void exit_itimers(struct signal_struct *);
 
 extern pid_t kernel_clone(struct kernel_clone_args *kargs);
-static inline long _do_fork(struct kernel_clone_args *kargs)
-{
-	return kernel_clone(kargs);
-}
 struct task_struct *fork_idle(int);
 struct mm_struct *copy_init_mm(void);
 extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);