x86/xen: do not use _PAGE_IOMAP in xen_remap_domain_mfn_range()

_PAGE_IOMAP is used in xen_remap_domain_mfn_range() to prevent the
pfn_pte() call in remap_area_mfn_pte_fn() from using the p2m to translate
the MFN.  If mfn_pte() is used instead, the p2m look up is avoided and
the use of _PAGE_IOMAP is no longer needed.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

arch/x86/xen/mmu.c

@@ -2522,7 +2522,7 @@ static int remap_area_mfn_pte_fn(pte_t *ptep, pgtable_t token,
 				 unsigned long addr, void *data)
 {
 	struct remap_data *rmd = data;
-	pte_t pte = pte_mkspecial(pfn_pte(rmd->mfn++, rmd->prot));
+	pte_t pte = pte_mkspecial(mfn_pte(rmd->mfn++, rmd->prot));
 
 	rmd->mmu_update->ptr = virt_to_machine(ptep).maddr;
 	rmd->mmu_update->val = pte_val_ma(pte);
@@ -2547,8 +2547,6 @@ int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return -EINVAL;
 
-	prot = __pgprot(pgprot_val(prot) | _PAGE_IOMAP);
-
 	BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) == (VM_PFNMAP | VM_IO)));
 
 	rmd.mfn = mfn;