cpu/SMT: create and export cpu_smt_possible()

mainline inclusion
from mainline-v5.4
commit e1572f1d
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6FB6C
CVE: CVE-2022-27672

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.3-rc1&id=e1572f1d08be57a5412a464cff0712a23cd0b73e



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KVM needs to know if SMT is theoretically possible, this means it is
supported and not forcefully disabled ('nosmt=force'). Create and
export cpu_smt_possible() answering this question.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Guo Mengqi <guomengqi3@huawei.com>
Reviewed-by: Wang Weiyang <wangweiyang2@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>