x86/EPT: consider page order when checking for APIC MFN

This was overlooked in 3d90d6e6 ("x86/EPT: split super pages upon
mismatching memory types").

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/mtrr.c
+++ b/xen/arch/x86/hvm/mtrr.c
@@ -816,15 +816,18 @@ int epte_get_entry_emt(struct domain *d,
           !has_arch_pdevs(d)) )
     {
         ASSERT(!direct_mmio ||
-               mfn_x(mfn) == d->arch.hvm_domain.vmx.apic_access_mfn);
+               !((mfn_x(mfn) ^ d->arch.hvm_domain.vmx.apic_access_mfn) >>
+                 order));
         *ipat = 1;
         return MTRR_TYPE_WRBACK;
     }
 
     if ( direct_mmio )
     {
-        if ( mfn_x(mfn) != d->arch.hvm_domain.vmx.apic_access_mfn )
+        if ( (mfn_x(mfn) ^ d->arch.hvm_domain.vmx.apic_access_mfn) >> order )
             return MTRR_TYPE_UNCACHABLE;
+        if ( order )
+            return -1;
         *ipat = 1;
         return MTRR_TYPE_WRBACK;
     }