btrfs: make flush_space take a enum btrfs_flush_state instead of int

I got a automated message from somebody who runs clang against our
kernels and it's because I used the wrong enum type for what I passed
into flush_space, caught by -Wenum-conversion.  Change the argument to
be explicitly the enum we're expecting to make everything consistent.
Maybe eventually gcc will catch errors like this.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/space-info.c

@@ -670,7 +670,7 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
  */
 static void flush_space(struct btrfs_fs_info *fs_info,
 		       struct btrfs_space_info *space_info, u64 num_bytes,
-		       int state)
+		       enum btrfs_flush_state state)
 {
 	struct btrfs_root *root = fs_info->extent_root;
 	struct btrfs_trans_handle *trans;
@@ -923,7 +923,7 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_space_info *space_info;
 	u64 to_reclaim;
-	int flush_state;
+	enum btrfs_flush_state flush_state;
 	int commit_cycles = 0;
 	u64 last_tickets_id;
 
@@ -1055,7 +1055,7 @@ static void btrfs_async_reclaim_data_space(struct work_struct *work)
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_space_info *space_info;
 	u64 last_tickets_id;
-	int flush_state = 0;
+	enum btrfs_flush_state flush_state = 0;
 
 	fs_info = container_of(work, struct btrfs_fs_info, async_data_reclaim_work);
 	space_info = fs_info->data_sinfo;