Form a single percpu.h from percpu_32.h and percpu_64.h. Both are now pretty
small so this is simply adding them together.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NMike Travis <travis@sgi.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>