hw: move CPU state serialization to migration/cpu.h

Remove usage of NEED_CPU_H from hw/hw.h.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/target-mips/machine.c b/target-mips/machine.c
index 22bca18..eb3d916 100644
--- a/target-mips/machine.c
+++ b/target-mips/machine.c
@@ -1,7 +1,7 @@
 #include "qemu/osdep.h"
 #include "hw/hw.h"
-
 #include "cpu.h"
+#include "migration/cpu.h"
 
 static int cpu_post_load(void *opaque, int version_id)
 {