x86, tlb, UV: Do small micro-optimization for native_flush_tlb_others()

native_flush_tlb_others() is called from:

 flush_tlb_current_task()
 flush_tlb_mm()
 flush_tlb_page()

All these functions disable preemption explicitly, so we can use
smp_processor_id() instead of get_cpu() and put_cpu().

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Cliff Wickman <cpw@sgi.com>
LKML-Reference: <4D7EC791.4040003@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>