percpu: remove PER_CPU_DEF_ATTRIBUTES macro

percpu: remove PER_CPU_DEF_ATTRIBUTES macro

The macro is not used:

  $ grep -r PER_CPU_DEF_ATTRIBUTES
  include/linux/percpu-defs.h:	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak		\
  include/linux/percpu-defs.h:	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES		\
  include/asm-generic/percpu.h:#ifndef PER_CPU_DEF_ATTRIBUTES
  include/asm-generic/percpu.h:#define PER_CPU_DEF_ATTRIBUTES

It was added with b01e8dc34379 ("alpha: fix percpu build breakage") and
removed in 2009 with b01e8dc34379..6088464cf1ae.

Link: http://lkml.kernel.org/r/20180821164904.qqhcduimjznods66@K55DR.localdomain
Signed-off-by: Alexander Pateenok <pateenoc@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>