net: hns3: Add support for ethtool -K to enable/disable HW GRO

This patch adds support of ethtool -K to enable/disable
hardware GRO in HNS3 PF/VF driver.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>