btrfs: Cleanup the "_struct" suffix in btrfs_workequeue

Since the "_struct" suffix is mainly used for distinguish the differnt
btrfs_work between the original and the newly created one,
there is no need using the suffix since all btrfs_workers are changed
into btrfs_workqueue.

Also this patch fixed some codes whose code style is changed due to the
too long "_struct" suffix.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Tested-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 6fa8219..751ee38 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -576,7 +576,7 @@
 	wake_up(&entry->wait);
 }
 
-static void btrfs_run_ordered_extent_work(struct btrfs_work_struct *work)
+static void btrfs_run_ordered_extent_work(struct btrfs_work *work)
 {
 	struct btrfs_ordered_extent *ordered;