net: hns3: use HNS3_NIC_STATE_RESETTING to indicate resetting

While hclge is going to reset, it will notify its client with
HNAE3_DOWN_CLIENT, so this client should get into a resetting
status from this moment, other operations from the stack need to
be blocked as well. And when the reset is finished, the client
will be notified with HNAE3_UP_CLIENT, so this is the end of
the resetting status.

This patch uses HNS3_NIC_STATE_RESETTING flag to implement that,
and adds hns3_nic_resetting() to indicate which operation is not
allowed.

Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>