zram: protect sysfs handler from invalid memory access

Date	Mon, 3 Jun 2013 23:42:20 +0800

Use zram->init_lock to protect access to zram->meta, otherwise it
may cause invalid memory access if zram->meta has been freed by
__zram_reset_device().

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Paul Reioux <reioux@gmail.com>