KVM: VMX: Use precomputed MAXPHYADDR for RTIT base MSR check

Use cpuid_maxphyaddr() instead of cpuid_query_maxphyaddr() for the
RTIT base MSR check.  There is no reason to recompute MAXPHYADDR as the
precomputed version is synchronized with CPUID updates, and
MSR_IA32_RTIT_OUTPUT_BASE is not written between stuffing CPUID and
refreshing vcpu->arch.maxphyaddr.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200924194250.19137-2-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>