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

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

Commit e73d57f6a73b ("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>