xen/arm and xen/arm64: implement HYPERVISOR_tmem_op

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 13609e0..f71c37e 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -314,4 +314,5 @@
 EXPORT_SYMBOL_GPL(HYPERVISOR_memory_op);
 EXPORT_SYMBOL_GPL(HYPERVISOR_physdev_op);
 EXPORT_SYMBOL_GPL(HYPERVISOR_vcpu_op);
+EXPORT_SYMBOL_GPL(HYPERVISOR_tmem_op);
 EXPORT_SYMBOL_GPL(privcmd_call);