[IA64] Unwire set/get_robust_list

The syscalls set/get_robust_list must not be wired up until
futex_atomic_cmpxchg_inatomic is implemented.  Otherwise the kernel will
hang in handle_futex_death.

Signed-off-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>