VT-d: correct off-by-1 in fault register range check

All our present implementation requires is that the range fully fits
in a single page. No need to exclude the case of the last register
extending right to the end of that page.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>

xen/drivers/passthrough/vtd/iommu.c

@@ -1273,7 +1273,7 @@ int __init iommu_alloc(struct acpi_drhd_unit *drhd)
     quirk_iommu_caps(iommu);
 
     if ( cap_fault_reg_offset(iommu->cap) +
-         cap_num_fault_regs(iommu->cap) * PRIMARY_FAULT_REG_LEN >= PAGE_SIZE ||
+         cap_num_fault_regs(iommu->cap) * PRIMARY_FAULT_REG_LEN > PAGE_SIZE ||
          ecap_iotlb_offset(iommu->ecap) >= PAGE_SIZE )
     {
         printk(XENLOG_ERR VTDPREFIX "IOMMU: unsupported\n");