keys: kill the dummy key_replace_session_keyring()

After the previouse change key_replace_session_keyring() becomes a nop.
Remove the dummy definition in key.h and update the callers in
arch/*/kernel/signal.c.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Gordeev <agordeev@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Smith <dsmith@redhat.com>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/key.h

@@ -33,8 +33,6 @@ typedef uint32_t key_perm_t;
 
 struct key;
 
-#define key_replace_session_keyring()	do { } while (0)
-
 #ifdef CONFIG_KEYS
 
 #undef KEY_DEBUGGING

include/linux/tracehook.h

@@ -186,8 +186,6 @@ static inline void set_notify_resume(struct task_struct *task)
  */
 static inline void tracehook_notify_resume(struct pt_regs *regs)
 {
-	if (current->replacement_session_keyring)
-		key_replace_session_keyring();
 	/*
 	 * The caller just cleared TIF_NOTIFY_RESUME. This barrier
 	 * pairs with task_work_add()->set_notify_resume() after