ub: uburma add cmd import/unimport segment implementation.

driver inclusion
category: feature
bugzilla: NA
CVE: NA

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Uburma add implementations of handling import/unimport segment cmd from
user layer.

This will make kernel possible to handle urma_import_seg and
urma_unimport_seg api in user-layer urma.

Import_seg will finally call ubcore_import_seg. The created target segment
will be related to a uobj.
Unimport seg will delete the tseg-related uobj. In uobj destroy function,
it will call ubcore_unimport_seg.

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