ACPI: Fix logic for removing mappings in 'acpi_unmap'

Make sure the removal of mappings uses the same logic that put the
mappings in place.

Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/osl.c

@@ -347,7 +347,7 @@ static void acpi_unmap(acpi_physical_address pg_off, void __iomem *vaddr)
 	unsigned long pfn;
 
 	pfn = pg_off >> PAGE_SHIFT;
-	if (page_is_ram(pfn))
+	if (should_use_kmap(pfn))
 		kunmap(pfn_to_page(pfn));
 	else
 		iounmap(vaddr);