iommu/vt-d: Use memunmap to free memremap

memunmap() should be used to free the return of memremap(), not
iounmap().

Fixes: dfddb969edf0 ('iommu/vt-d: Switch from ioremap_cache to memremap')
Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -3075,7 +3075,7 @@ static int copy_context_table(struct intel_iommu *iommu,
 			}
 
 			if (old_ce)
-				iounmap(old_ce);
+				memunmap(old_ce);
 
 			ret = 0;
 			if (devfn < 0x80)