net: hns3: fix GRE checksum offload issue

The device_version V3 hardware can't offload the checksum for IP in GRE
packets, but can do it for NvGRE. So default to disable the checksum and
GSO offload for GRE, but keep the ability to enable it when only using
NvGRE.

Fixes: 76ad4f0e ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Jie Wang <wangjie125@huawei.com>
Signed-off-by: Jijie Shao <shaojijie@huawei.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>