[S390] Wire up epoll_pwait syscall.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

arch/s390/kernel/syscalls.S

@@ -320,3 +320,4 @@ SYSCALL(sys_tee,sys_tee,sys_tee_wrapper)
 SYSCALL(sys_vmsplice,sys_vmsplice,compat_sys_vmsplice_wrapper)
 NI_SYSCALL							/* 310 sys_move_pages */
 SYSCALL(sys_getcpu,sys_getcpu,sys_getcpu_wrapper)
+SYSCALL(sys_epoll_pwait,sys_epoll_pwait,sys_ni_syscall)