x86-xen_domu: remove

Remove obsolete x86-xen_domu definition, it has been merged into
x86-generic.

targets/targets.mk

@@ -7,7 +7,6 @@ $(eval $(call GluonTarget,mpc85xx,generic))
 $(eval $(call GluonTarget,x86,generic))
 $(eval $(call GluonTarget,x86,geode))
 $(eval $(call GluonTarget,x86,64))
-$(eval $(call GluonTarget,x86,xen_domu))
 
 ifneq ($(BROKEN),)
 $(eval $(call GluonTarget,ar71xx,mikrotik)) # BROKEN: no sysupgrade support

targets/x86-xen_domu

-factory_image x86-xen combined-ext4 .img.gz
-sysupgrade_image x86-xen combined-ext4 .img.gz