signalfd: fix undefined reference to `compat_sys_signalfd4' when !CONFIG_SIGNALFD

fix:

arch/x86/ia32/built-in.o: In function `ia32_sys_call_table':
(.rodata+0xa38): undefined reference to `compat_sys_signalfd4'

on !CONFIG_SIGNALFD.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/sys_ni.c

@@ -160,6 +160,7 @@ cond_syscall(sys_ioprio_get);
 cond_syscall(sys_signalfd);
 cond_syscall(sys_signalfd4);
 cond_syscall(compat_sys_signalfd);
+cond_syscall(compat_sys_signalfd4);
 cond_syscall(sys_timerfd_create);
 cond_syscall(sys_timerfd_settime);
 cond_syscall(sys_timerfd_gettime);