x86/xen_domu: enable image generation

Add features ext4 targz to target x86/xen_domu in order to
generate images in defconfig.

This fixes #18074.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>

SVN-Revision: 46233

target/linux/x86/xen_domu/target.mk

@@ -1,3 +1,3 @@
 BOARDNAME:=Xen Paravirt Guest
 DEFAULT_PACKAGES += kmod-xen-fs kmod-xen-evtchn kmod-xen-netdev kmod-xen-kbddev
-FEATURES:=display
+FEATURES:=display ext4 targz