[DMA]: Fix example code in DMA-mapping.txt

Spotted by Jack Spaar <jspaar@myrealbox.com>
Signed-off-by: David S. Miller <davem@redhat.com>

Documentation/DMA-mapping.txt

@@ -222,14 +222,14 @@ Here is pseudo-code showing how this might be done:
 	struct pci_dev *pdev;
 
 	...
-	if (pci_set_dma_mask(pdev, PLAYBACK_ADDRESS_BITS)) {
+	if (!pci_set_dma_mask(pdev, PLAYBACK_ADDRESS_BITS)) {
 		card->playback_enabled = 1;
 	} else {
 		card->playback_enabled = 0;
 		printk(KERN_WARN "%s: Playback disabled due to DMA limitations.\n",
 		       card->name);
 	}
-	if (pci_set_dma_mask(pdev, RECORD_ADDRESS_BITS)) {
+	if (!pci_set_dma_mask(pdev, RECORD_ADDRESS_BITS)) {
 		card->record_enabled = 1;
 	} else {
 		card->record_enabled = 0;