x86/percpu: Move cpu_number next to current_task

Also add cpu_number to the pcpu_hot structure, it is often referenced
and this cacheline is there.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111145.387678283@infradead.org