net: spnic: add NIC layer

Ramaxel inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4CBDP


CVE: NA

Add NIC Layer support, include:
1. register net device to the kernel
2. implement the hooks of the 'struct net_device_ops' and
    'struct ethtool_ops'
3. etc.

Signed-off-by: Yanling Song <songyl@ramaxel.com>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>