m25p80: add missing blk_attach_dev_nofail

m25p80: add missing blk_attach_dev_nofail

Of the block devices that poked into -drive options via drive_get_next,
m25p80 was the only one who also did not attach itself to the BlockBackend.

Since sd does it, and all other devices go through a "drive" property,
with this change all block backends attached to the guest will have a
non-NULL result for blk_get_attached_dev().

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 1429025387-11077-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>