net: hns3: add support for mapping device memory

For device who has device memory accessed through the PCI BAR4,
IO descriptor push of NIC and direct WQE(Work Queue Element) of
RoCE will use this device memory, so add support for mapping
this device memory, and add this info to the RoCE client whose
new feature needs.

Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>