block: Attach non-qdev devices as well

For now, this just protects against programming errors like having the
same drive back multiple non-qdev devices, or untimely bdrv_delete().
Later commits will add other interesting uses.

While there, rename BlockDriverState member peer to dev, bdrv_attach()
to bdrv_attach_dev(), bdrv_detach() to bdrv_detach_dev(), and
bdrv_get_attached() to bdrv_get_attached_dev().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 2602591..049dda5 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -14,7 +14,6 @@
 #include "qemu-option.h"
 #include "qemu-config.h"
 #include "sysemu.h"
-#include "hw/qdev.h"
 #include "block_int.h"
 
 static QTAILQ_HEAD(drivelist, DriveInfo) drives = QTAILQ_HEAD_INITIALIZER(drives);
@@ -738,12 +737,12 @@
     bdrv_flush(bs);
     bdrv_close(bs);
 
-    /* if we have a device associated with this BlockDriverState (bs->peer)
+    /* if we have a device attached to this BlockDriverState
      * then we need to make the drive anonymous until the device
      * can be removed.  If this is a drive with no device backing
      * then we can just get rid of the block driver state right here.
      */
-    if (bs->peer) {
+    if (bdrv_get_attached_dev(bs)) {
         bdrv_make_anon(bs);
     } else {
         drive_uninit(drive_get_by_blockdev(bs));