x86: page.h: make pte_t a union to always include

Make sure pte_t, whatever its definition, has a pte element with type
pteval_t.  This allows common code to access it without needing to be
specifically parameterised on what pagetable mode we're compiling for.
For 32-bit, this means that pte_t becomes a union with "pte" and "{
pte_low, pte_high }" (PAE) or just "pte_low" (non-PAE).

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 0ac6c5d..52f3928 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -244,9 +244,7 @@
 	if (pte & 1)
 		pte = phys_to_machine(XPADDR(pte)).maddr;
 
-	pte &= ~_PAGE_PCD;
-
-	return (pte_t){ pte, pte >> 32 };
+	return (pte_t){ .pte = pte };
 }
 
 pmd_t xen_make_pmd(unsigned long long pmd)