xen: move the xenvm machine to mach-virt

xenvm is based on mach-vexpress, move it to mach-virt.

Changes in v4:
- update the dts Makefile too.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: Marc Zyngier <marc.zyngier@arm.com>
CC: will.deacon@arm.com
CC: arnd@arndb.de
CC: rob.herring@calxeda.com
diff --git a/arch/arm/boot/dts/Makefile b/arch/arm/boot/dts/Makefile
index 9c62558..b6289b76 100644
--- a/arch/arm/boot/dts/Makefile
+++ b/arch/arm/boot/dts/Makefile
@@ -168,8 +168,8 @@
 dtb-$(CONFIG_ARCH_VEXPRESS) += vexpress-v2p-ca5s.dtb \
 	vexpress-v2p-ca9.dtb \
 	vexpress-v2p-ca15-tc1.dtb \
-	vexpress-v2p-ca15_a7.dtb \
-	xenvm-4.2.dtb
+	vexpress-v2p-ca15_a7.dtb
+dtb-$(CONFIG_ARCH_VIRT) += xenvm-4.2.dtb
 dtb-$(CONFIG_ARCH_VT8500) += vt8500-bv07.dtb \
 	wm8505-ref.dtb \
 	wm8650-mid.dtb \