net: hns3: fix for returning wrong value problem in hns3_get_rss_indir_size

The return type of hns3_get_rss_indir_size is u32. But a negative value is
returned. This patch fixes it by replacing the negative value with zero.

Signed-off-by: Fuyun Liang <liangfuyun1@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>