net: hns3: check resetting status in hns3_get_stats()

hns3_get_stats() should check the resetting status firstly,
since the device will be reinitialized when resetting. If the
reset has not completed, the hns3_get_stats() may access
invalid memory.

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