KVM: X86: Delay read msr data iff writes ICR MSR

Delay read msr data until we identify guest accesses ICR MSR to avoid
to penalize all other MSR writes.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1585189202-1708-2-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>