dma-pool: no need to check return value of debugfs_create functions

When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

kernel/dma/pool.c

@@ -38,9 +38,6 @@ static void __init dma_atomic_pool_debugfs_init(void)
 	struct dentry *root;
 
 	root = debugfs_create_dir("dma_pools", NULL);
-	if (IS_ERR_OR_NULL(root))
-		return;
-
 	debugfs_create_ulong("pool_size_dma", 0400, root, &pool_size_dma);
 	debugfs_create_ulong("pool_size_dma32", 0400, root, &pool_size_dma32);
 	debugfs_create_ulong("pool_size_kernel", 0400, root, &pool_size_kernel);