qdev: add return value to init() callbacks.

Sorry folks, but it has to be.  One more of these invasive qdev patches.

We have a serious design bug in the qdev interface:  device init
callbacks can't signal failure because the init() callback has no
return value.  This patch fixes it.

We have already one case in-tree where this is needed:
Try -device virtio-blk-pci (without drive= specified) and watch qemu
segfault.  This patch fixes it.

With usb+scsi being converted to qdev we'll get more devices where the
init callback can fail for various reasons.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/sbi.c b/hw/sbi.c
index e6ced8b..bad9afd 100644
--- a/hw/sbi.c
+++ b/hw/sbi.c
@@ -131,7 +131,7 @@
     }
 }
 
-static void sbi_init1(SysBusDevice *dev)
+static int sbi_init1(SysBusDevice *dev)
 {
     SBIState *s = FROM_SYSBUS(SBIState, dev);
     int sbi_io_memory;
@@ -148,6 +148,7 @@
     register_savevm("sbi", -1, 1, sbi_save, sbi_load, s);
     qemu_register_reset(sbi_reset, s);
     sbi_reset(s);
+    return 0;
 }
 
 static SysBusDeviceInfo sbi_info = {