btrfs: Use WARN_ON()'s return value in place of WARN_ON(1)

Use WARN_ON()'s return value in place of WARN_ON(1) for cleaner source
code that outputs a more descriptive warnings. Also fix the styling
warning of redundant braces that came up as a result of this fix.

Signed-off-by: Dulshani Gunawardhana <dulshani.gunawardhana89@gmail.com>
Reviewed-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 7927a5f..744553c 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2130,8 +2130,7 @@
 		WARN_ON(*level >= BTRFS_MAX_LEVEL);
 		cur = path->nodes[*level];
 
-		if (btrfs_header_level(cur) != *level)
-			WARN_ON(1);
+		WARN_ON(btrfs_header_level(cur) != *level);
 
 		if (path->slots[*level] >=
 		    btrfs_header_nritems(cur))
@@ -2951,10 +2950,8 @@
 
 	/* find the first key from this transaction again */
 	ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
-	if (ret != 0) {
-		WARN_ON(1);
+	if (WARN_ON(ret != 0))
 		goto done;
-	}
 
 	/*
 	 * we have a block from this transaction, log every item in it