Enable hotplug support on hi3xxx platform

How to test:
cat proc/interrupts
echo 0 > /sys/devices/system/cpu/cpuX/online
cat proc/interrupts
echo 1 > /sys/devices/system/cpu/cpuX/online
Signed-off-by: NZhangfei Gao <zhangfei.gao@linaro.org>
Tested-by: NZhang Mingjun <zhang.mingjun@linaro.org>
Signed-off-by: NHaojian Zhuang <haojian.zhuang@linaro.org>
[khilman: fixed checkpatch error]
Signed-off-by: NKevin Hilman <khilman@linaro.org>