posix-timers: move the initialization of timer->sigq from send to create path

posix_timer_event() always populates timer->sigq with the same numbers,
move this code into sys_timer_create().

Note that with this patch we can kill it_sigev_signo and it_sigev_value.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>