ub: add alloc/free ucontext ops in ubcore

driver inclusion
category: feature
bugzilla: NA
CVE: NA

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The UB Core invokes the UBN driver to
create a URMA context and set the uasid value.

Input parameter:
dev: UB device for creating the context.
eid: specifies an EID to create a context.
udrv_data: address of the private data exchanged
between the UBN user-mode driver and kernel-mode driver,
including the address of the urma context.

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