KVM: cpuid: do_cpuid_ent works on a whole CPUID function

mainline inclusion
from mainline-v5.3-rc1
commit ab8bcf64
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I3YAEG


CVE: NA

-----------------------------

Rename it as well as __do_cpuid_ent and __do_cpuid_ent_emulated to have
"func" in its name, and drop the index parameter which is always 0.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jingyi Wang <wangjingyi11@huawei.com>
Reviewed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>