build: remove universal-obj-y

All of universal-obj-y, user-obj-y (right now unused) and common-obj-y can
be unified into common-obj-y if we take care of defining CONFIG_SOFTMMU
and CONFIG_USER_ONLY in the toplevel makefile.  This is similar to how
we define symbols for hardware components.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/qom/Makefile.objs b/qom/Makefile.objs
index 1899a4c..6a93ac7 100644
--- a/qom/Makefile.objs
+++ b/qom/Makefile.objs
@@ -1,2 +1,2 @@
-universal-obj-y = object.o container.o qom-qobject.o
-universal-obj-y += cpu.o
+common-obj-y = object.o container.o qom-qobject.o
+common-obj-y += cpu.o