[DECLARE|DEFINE]_PER_CPU_MULTIPAGE_ALIGNED never really worked because
the head percpu section was only page aligned. Now that the last user
is gone (32-bit IRQ stacks), remove the generic percpu facility.

Cc: Brian Gerst <brgerst@gmail.com>
Acked-by: NTejun Heo <tj@kernel.org>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1288158182-1753-1-git-send-email-brgerst@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>