ub: ubcore add register/unregister seg api.

driver inclusion
category: feature
bugzilla: NA
CVE: NA

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Ubcore add register/unregister seg api, which will finally call hw driver's
registered method register/unregister seg.

register_seg:
The UB Core invokes the UBN driver to register the segment and key.
Input parameter:
dev: UB device that registers the segment.
cfg: basic information about the segment to be registered.
udata: contains the pointer of the URMA context and the address of the
private data exchanged between the UBN user-mode driver and
kernel-mode driver.
Output parameter:
None.
Return value:
If the registration is successful, the segment structure pointer is
returned. The returned information includes the segment key ID.
The registration fails and NULL is returned.

unregister_seg:
The UB Core invokes the UBN driver to deregister the segment and ukey.
Input parameter:
tseg: pointer to the target segment to be deregistered
Return value:
The value 0 indicates that the deregistration is successful,
and other values indicate that the deregistration fails.

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