block: Make bdrv_states public

block: Make bdrv_states public

When inserting a BDS tree into a BB, we will need to add the root BDS to
this list. Since we will want to do that in the blockdev-insert-medium
implementation in blockdev.c, we will need access to it there.

This patch is not exactly elegant, but bdrv_states will be removed in
the future anyway because we no longer need it since we have BBs.

Signed-off-by: Max Reitz <[email protected]>
Reviewed-by: Alberto Garcia <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>