ub: Add register device api in ubcore

driver inclusion
category: feature
bugzilla: NA
CVE: NA

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Add register device api in ubcore.

This interface is invoked during UBN driver loading and initialization
to register the UB device with the UB Core protocol layer.

Input parameter:
dev: The structure contains netdev, device name, ops,
and vendor-defined device private data.
Device names of different functions of the same vendor must be unique.
Deduplicated by the protocol stack.
The memory of ubcore_device_t is allocated by the UBN driver.

Return value:
The value 0 indicates that the registration is successful.
Other values indicate that the registration fails.

Signed-off-by: Guoxin Qian <qianguoxin@huawei.com>
Signed-off-by: Yizhen Fan <fanyizhen@huawei.com>