svm: driver probe to read l2buff addr

ascend inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4JMM0


CVE: NA

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svm probe to read l2buff addr and size, this is rts
to set l2buff

Signed-off-by: Lijun Fang <fanglijun3@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>