block: Make BlockDriver method bdrv_eject() return void

Callees always return 0, except for FreeBSD's cdrom_eject(), which
returns -ENOTSUP when the device is in a terminally wedged state.

The only caller is bdrv_eject(), and it maps -ENOTSUP to 0 since
commit 4be9762a.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block_int.h b/block_int.h
index e0b638c..efefbee 100644
--- a/block_int.h
+++ b/block_int.h
@@ -112,7 +112,7 @@
     /* removable device specific */
     int (*bdrv_is_inserted)(BlockDriverState *bs);
     int (*bdrv_media_changed)(BlockDriverState *bs);
-    int (*bdrv_eject)(BlockDriverState *bs, int eject_flag);
+    void (*bdrv_eject)(BlockDriverState *bs, int eject_flag);
     void (*bdrv_set_locked)(BlockDriverState *bs, int locked);
 
     /* to control generic scsi devices */