Commit:

  a7be6e5a ("mm: drop useless local parameters of __register_one_node()")

... removed the last user of parent_node(), so remove the macro.
Reported-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NDou Liyang <douly.fnst@cn.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1501076076-1974-11-git-send-email-douly.fnst@cn.fujitsu.comSigned-off-by: NIngo Molnar <mingo@kernel.org>