net: hns3: revert to old channel when setting new channel num fail

After setting new channel num, it needs free old ring memory and
allocate new ring memory. If there is no enough memory and allocate
new ring memory fail, the ring may initialize fail. To make sure
the network interface can work normally, driver should revert the
channel to the old configuration.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>