btrfs: remove unused member btrfs_device::work

This is a leftover from recently removed bio scheduling framework.

Fixes: ba8a9d079543 ("Btrfs: delete the entire async bio submission framework")
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
1 file changed