Force tick interrupt and get rid of softirq magic

Force tick interrupt and get rid of softirq magic

This is a backporting from upstream linux, please refer to
http://marc.info/?t=142904577100001&r=1&w=2 for more information, the
corresponding kernel commit is 0ff53d09642204c64842 (tick: sched: Force
tick interrupt and get rid of softirq magic).

The purpose of this patch is, if a tick_sched interrupt is missed, don't
try to raise softirq, instead, we can simply trigger the timer interrupt.
The reason is, softirq requires context switch and has much higher overhead
than interrupt.

Upstream status: backport 0ff53d09642204c64842

Change-Id: I70131fb85189d15972fcaa1a2a2fa190270787f9
Back-port-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>