x86: set strong uncacheable where UC is really desired

Also use _PAGE_PWT for all the mappings which need uncache mapping.
Instead of existing PAT2 which is UC- (and can be overwritten by MTRRs),
we now use PAT3 which is strong uncacheable.

This makes it consistent with pgprot_noncached()
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/mm/ioremap_32.c

@@ -119,7 +119,7 @@ EXPORT_SYMBOL(__ioremap);
 void __iomem *ioremap_nocache (unsigned long phys_addr, unsigned long size)
 {
 	unsigned long last_addr;
-	void __iomem *p = __ioremap(phys_addr, size, _PAGE_PCD);
+	void __iomem *p = __ioremap(phys_addr, size, _PAGE_PCD | _PAGE_PWT);
 	if (!p) 
 		return p; 
 

arch/x86/mm/ioremap_64.c

@@ -138,7 +138,7 @@ EXPORT_SYMBOL(__ioremap);
 
 void __iomem *ioremap_nocache (unsigned long phys_addr, unsigned long size)
 {
-	return __ioremap(phys_addr, size, _PAGE_PCD);
+	return __ioremap(phys_addr, size, _PAGE_PCD | _PAGE_PWT);
 }
 EXPORT_SYMBOL(ioremap_nocache);