mem-hotplug: introduce MMOP_OFFLINE to replace the hard coding -1

mem-hotplug: introduce MMOP_OFFLINE to replace the hard coding -1

In store_mem_state(), we have:
......
 334         else if (!strncmp(buf, "offline", min_t(int, count, 7)))
 335                 online_type = -1;
......
 355         case -1:
 356                 ret = device_offline(&mem->dev);
 357                 break;
......

Here, "offline" is hard coded as -1.

This patch does the following renaming:
 ONLINE_KEEP     ->  MMOP_ONLINE_KEEP
 ONLINE_KERNEL   ->  MMOP_ONLINE_KERNEL
 ONLINE_MOVABLE  ->  MMOP_ONLINE_MOVABLE

and introduce MMOP_OFFLINE = -1 to avoid hard coding.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Hu Tao <hutao@cn.fujitsu.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>