explicitly include hw/qdev-core.h

exec/cpu-all.h includes qom/cpu.h, which includes hw/qdev-core.h.
Explicit inclusion will keep things working when cpu.h will not be
included indirectly almost everywhere (either directly or through
qemu-common.h).
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

bootdevice.c

@@ -28,6 +28,7 @@
 #include "qapi/visitor.h"
 #include "qemu/error-report.h"
 #include "hw/hw.h"
+#include "hw/qdev-core.h"
 
 typedef struct FWBootEntry FWBootEntry;