dma-debug: make things less spammy under memory pressure

Limit the error msg to avoid flooding the console.  If you have a lot of
threads hitting this at once, they could have already gotten passed the
dma_debug_disabled() check before they get to the point of allocation
failure, resulting in quite a lot of this error message spamming the
log.  Use pr_err_once() to limit that.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

kernel/dma/debug.c

@@ -564,7 +564,7 @@ static void add_dma_entry(struct dma_debug_entry *entry, unsigned long attrs)
 
 	rc = active_cacheline_insert(entry);
 	if (rc == -ENOMEM) {
-		pr_err("cacheline tracking ENOMEM, dma-debug disabled\n");
+		pr_err_once("cacheline tracking ENOMEM, dma-debug disabled\n");
 		global_disable = true;
 	} else if (rc == -EEXIST && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
 		err_printk(entry->dev, entry,