block: drop unused bdrv_clear_incoming_migration_all() prototype

The bdrv_clear_incoming_migration_all() function has not existed since
commit 7ea2d269 ("block/migration:
Disable cache invalidate for incoming migration").
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1418212937-22222-1-git-send-email-stefanha@redhat.com

include/block/block.h

@@ -329,8 +329,6 @@ BlockAIOCB *bdrv_aio_ioctl(BlockDriverState *bs,
 void bdrv_invalidate_cache(BlockDriverState *bs, Error **errp);
 void bdrv_invalidate_cache_all(Error **errp);
 
-void bdrv_clear_incoming_migration_all(void);
-
 /* Ensure contents are flushed to disk.  */
 int bdrv_flush(BlockDriverState *bs);
 int coroutine_fn bdrv_co_flush(BlockDriverState *bs);