arch/ia64/include/asm/topology.h: remove unused parent_node() macro

Commit a7be6e5a7f8d ("mm: drop useless local parameters of
__register_one_node()") removed the last user of parent_node().

The parent_node() macro in IA64(Itanium) platform is unnecessary.

Remove it for cleanup.

Link: http://lkml.kernel.org/r/1504234599-29533-2-git-send-email-douly.fnst@cn.fujitsu.com
Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/ia64/include/asm/topology.h

@@ -33,13 +33,6 @@
 			       cpu_all_mask :				\
 			       &node_to_cpu_mask[node])
 
-/*
- * Returns the number of the node containing Node 'nid'.
- * Not implemented here. Multi-level hierarchies detected with
- * the help of node_distance().
- */
-#define parent_node(nid) (nid)
-
 /*
  * Determines the node for a given pci bus
  */