iommu/amd: Free domain id when free a domain of struct dma_ops_domain

BugLink: http://bugs.launchpad.net/bugs/1642968

commit c3db901c upstream.

The current code missed freeing domain id when free a domain of
struct dma_ops_domain.
Signed-off-by: Baoquan He <bhe@redhat.com>
Fixes: ec487d1a ('x86, AMD IOMMU: add domain allocation and deallocation functions')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/iommu/amd_iommu.c

@@ -1833,6 +1833,9 @@ static void dma_ops_domain_free(struct dma_ops_domain *dom)
 		kfree(dom->aperture[i]);
 	}
 
+	if (dom->domain.id)
+		domain_id_free(dom->domain.id);
+
 	kfree(dom);
 }