block: move bdi/address_space unplug functions to backing-dev.h
Jens Axboe authored

There's nothing block related about them, the backing device
is used by things like NFS etc as well. This gets rid of the
need to protect such calls by CONFIG_BLOCK.
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
b9d128f1