signal: Make kill_proc_info static

There are no users outside of signal.c so make the function static so
the compiler and other developers have that information.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

include/linux/sched/signal.h

@@ -293,7 +293,6 @@ extern int kill_pid_info_as_cred(int, struct siginfo *, struct pid *,
 				const struct cred *, u32);
 extern int kill_pgrp(struct pid *pid, int sig, int priv);
 extern int kill_pid(struct pid *pid, int sig, int priv);
-extern int kill_proc_info(int, struct siginfo *, pid_t);
 extern __must_check bool do_notify_parent(struct task_struct *, int);
 extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
 extern void force_sig(int, struct task_struct *);

kernel/signal.c

@@ -1318,7 +1318,7 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
 	}
 }
 
-int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
+static int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
 {
 	int error;
 	rcu_read_lock();