signal: use kill_proc_info instead of kill_pid_info in kill_something_info

signal.c provides kill_proc_info, we can use it instead of kill_pid_info
in kill_something_info func gracefully.

Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/80236965-f0b5-c888-95ff-855bdec75bb3@huawei.com


Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>