xen/tmem: do not allow XEN_TMEM on ARM64

tmem is not supported on arm or arm64 yet. Will revert this
once the Xen hypervisor supports it.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 9e02d60..23eae5c 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -145,7 +145,7 @@
 
 config XEN_TMEM
 	tristate
-	depends on !ARM
+	depends on !ARM && !ARM64
 	default m if (CLEANCACHE || FRONTSWAP)
 	help
 	  Shim to interface in-kernel Transcendent Memory hooks