[IA64] use generic compat_old_sys_readdir

Switch ia64 to the generic compat_sys_old_readdir which is identical
except for slightly better error handling.  Also remove sys32_getdents
which already isn't wired up to the syscall table anymore in favour of
compat_sys_getdents.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>