ACPI: consistently use should_use_kmap()

... so that acpi_unmap()'s behavior gets in sync with acpi_map()'s.
Signed-off-by: Jan Beulich <jbeulich@suse.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);