kvm: make KVM_CAP_ENABLE_CAP_VM architecture agnostic

mainline inclusion
from mainline-v5.0
commit: e5d83c74
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I66COX
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.10.y&id=e5d83c74a5800c2a1fa3ba982c1c4b2b39ae6db2



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The first such capability to be handled in virt/kvm/ will be manual
dirty page reprotection.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>