[IA64] fix paravirtualization of clone2() system call.

[IA64] fix paravirtualization of clone2() system call.

If audit is enabled or the child process is ptraced,
non-paravirtualized code path is executed.
Thus paravirtualized ifs is left unmodifed so that the child process
crashes after clone2().
paravirtualize ia64_ret_from_clone() to fix it.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>