KVM: VMX: Use precomputed vmx->pt_desc.addr_range

The number of valid PT ADDR MSRs for the guest is precomputed in
vmx->pt_desc.addr_range. Use it instead of calculating again.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-Id: <20210827070249.924633-3-xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>