btrfs: use cond_resched_lock where possible

Clean the opencoded variant, cond_resched_lock also checks the lock for
contention so it might help in some cases that were not covered by
simple need_resched().

Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index a719785..96611fe 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2402,11 +2402,8 @@
 		} else {
 			free_bitmap(ctl, info);
 		}
-		if (need_resched()) {
-			spin_unlock(&ctl->tree_lock);
-			cond_resched();
-			spin_lock(&ctl->tree_lock);
-		}
+
+		cond_resched_lock(&ctl->tree_lock);
 	}
 }
 
@@ -2431,11 +2428,8 @@
 
 		WARN_ON(cluster->block_group != block_group);
 		__btrfs_return_cluster_to_free_space(block_group, cluster);
-		if (need_resched()) {
-			spin_unlock(&ctl->tree_lock);
-			cond_resched();
-			spin_lock(&ctl->tree_lock);
-		}
+
+		cond_resched_lock(&ctl->tree_lock);
 	}
 	__btrfs_remove_free_space_cache_locked(ctl);
 	spin_unlock(&ctl->tree_lock);