net: hns: fix port unavailable after hnae_reserve_buffer_map fail

When hnae_reserve_buffer_map fail, it will break cycle and some
buffer description has no available memory, therefore the port will
be unavailable.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Reviewed-by: Yisen Zhuang <yisen.zhuang@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>