qdev: Simplify the SysBusDeviceClass::init path

Instead of using
  SysBusDeviceClass::realize
   -> DeviceClass::realize
       -> DeviceClass::init
           -> sysbus_device_init
              -> SysBusDeviceClass::init

Simplify the path by directly calling SysBusDeviceClass::init
in SysBusDeviceClass::realize:

  SysBusDeviceClass::realize
   -> SysBusDeviceClass::init

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180419212727.26095-4-f4bug@amsat.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Removal of DeviceClass::init() moved into next patch,
sysbus_realize() tweaked for clarity]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180528144509.15812-4-armbru@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/core/sysbus.c

@@ -18,6 +18,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/error.h"
 #include "hw/sysbus.h"
 #include "monitor/monitor.h"
 #include "exec/address-spaces.h"
@@ -200,15 +201,18 @@ void sysbus_init_ioports(SysBusDevice *dev, uint32_t ioport, uint32_t size)
     }
 }
 
-static int sysbus_device_init(DeviceState *dev)
+/* TODO remove once all sysbus devices have been converted to realize */
+static void sysbus_realize(DeviceState *dev, Error **errp)
 {
     SysBusDevice *sd = SYS_BUS_DEVICE(dev);
     SysBusDeviceClass *sbc = SYS_BUS_DEVICE_GET_CLASS(sd);
 
     if (!sbc->init) {
-        return 0;
+        return;
+    }
+    if (sbc->init(sd) < 0) {
+        error_setg(errp, "Device initialization failed");
     }
-    return sbc->init(sd);
 }
 
 DeviceState *sysbus_create_varargs(const char *name,
@@ -324,7 +328,7 @@ MemoryRegion *sysbus_address_space(SysBusDevice *dev)
 static void sysbus_device_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *k = DEVICE_CLASS(klass);
-    k->init = sysbus_device_init;
+    k->realize = sysbus_realize;
     k->bus_type = TYPE_SYSTEM_BUS;
     /*
      * device_add plugs devices into a suitable bus.  For "real" buses,