livepatch: put memory alloc and free out stop machine

hulk inclusion
category: feature
bugzilla: 51924
CVE: NA

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When a livepatch is insmod, stop machine will stop other cores, which
interrupts services. Therefore, the shorter the stop machine duration,
the better. The application and release of memory from the stop machine
can shorten the time for stopping the machine.

Especially, module_alloc and module_memfree is a kind of vmalloc, that
may sleep when called. So it is not permitted to use them in stop machine
context.

Signed-off-by: Ye Weihua <yeweihua4@huawei.com>
Reviewed-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>