x86_64: use signalfd and timerfd compat syscalls

Looks like these two are wired up in a wrong way.

Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>