hw: Clean "hw/devices.h" includes

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180528232719.4721-22-f4bug@amsat.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/hw/devices.h

 #ifndef QEMU_DEVICES_H
 #define QEMU_DEVICES_H
 
-#include "hw/irq.h"
-
-/* ??? Not all users of this file can include cpu-common.h.  */
-struct MemoryRegion;
-
 /* Devices that have nowhere better to go.  */
 
+#include "hw/hw.h"
+
 /* smc91c111.c */
 void smc91c111_init(NICInfo *, uint32_t, qemu_irq);