ub: uburma add cmd register/unregister segment implementation.

driver inclusion
category: feature
bugzilla: NA
CVE: NA

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Uburma add implementations of handling register/unregister segment cmd from
user layer.

This will make kernel possible to handle urma_register_seg and
urma_unregister_seg api in user-layer urma.

Register_seg will finally call ubcore_register_seg. The created segment
will be related to a uobj.
Unregister seg will delete the seg-related uobj. In uobj destroy function,
it will call ubcore_unregister_seg.

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