btrfs: Fix checkpatch.pl warning of spacing issues

Fix spacing issues detected via checkpatch.pl in accordance with the
kernel style guidelines.

Signed-off-by: Dulshani Gunawardhana <dulshani.gunawardhana89@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 08cc08f..8aec751 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -262,7 +262,7 @@
 	struct btrfs_work *work = NULL;
 	struct list_head *cur = NULL;
 
-	if(!list_empty(prio_head))
+	if (!list_empty(prio_head))
 		cur = prio_head->next;
 
 	smp_mb();