hw/core: Move null-machine into the common-obj list

The null-machine code used to be target specific since it used the
target-specific cpu_init() function in the past. But in the recent
commit 2278b93941d42c30e2950 ("Use cpu_create(type) instead of
cpu_init(cpu_model)") this has been change, so that the code now
uses the common cpu_create() function instead. Thus we can put
the null-machine into the common-obj list so that it is compiled
only once for all targets, to save some compilation time.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/core/Makefile.objs

@@ -21,5 +21,4 @@ common-obj-$(CONFIG_SOFTMMU) += or-irq.o
 common-obj-$(CONFIG_SOFTMMU) += split-irq.o
 common-obj-$(CONFIG_PLATFORM_BUS) += platform-bus.o
 common-obj-$(CONFIG_SOFTMMU) += generic-loader.o
-
-obj-$(CONFIG_SOFTMMU) += null-machine.o
+common-obj-$(CONFIG_SOFTMMU) += null-machine.o

hw/core/null-machine.c

@@ -18,7 +18,7 @@
 #include "hw/boards.h"
 #include "sysemu/sysemu.h"
 #include "exec/address-spaces.h"
-#include "cpu.h"
+#include "qom/cpu.h"
 
 static void machine_none_init(MachineState *mch)
 {