blk-mq: change gfp flags to GFP_NOIO in blk_mq_realloc_hw_ctxs

mainline inclusion
from mainline-4.20-rc1
commit 5b202853
category: bugfix
bugzilla: 5833
CVE: NA
---------------------------

blk_mq_realloc_hw_ctxs could be invoked during update hw queues.
At the momemt, IO is blocked. Change the gfp flags from GFP_KERNEL
to GFP_NOIO to avoid forever hang during memory allocation in
blk_mq_realloc_hw_ctxs.

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>