ub: Add register/unregister client api in ubcore

driver inclusion
category: feature
bugzilla: NA
CVE: NA

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Add register/unregister client api in ubcore

This api will be used by client of ubcore,
which call this api to register as a client of ubcore

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