net: hns3: add get/set_coalesce support to VF

This patch adds ethtool_ops.get/set_coalesce support to VF.

Since PF and VF share the same get/set_coalesce interface,
we only need to set hns3_get/set_coalesce to the ethtool_ops
when supporting get/set_coalesce for VF.

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>