thunderbolt: Remove useless DMA-32 fallback configuration

As stated in [1], dma_set_mask() with a 64-bit mask never fails if
dev->dma_mask is non-NULL.
So, if it fails, the 32 bits case will also fail for the same reason.

Simplify code and remove some dead code accordingly.

While at it, include directly <linux/dma-mapping.h> instead on relying on
indirect inclusion.

[1]: https://lkml.org/lkml/2021/6/7/398

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/nhi.c

@@ -13,6 +13,7 @@
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/pci.h>
+#include <linux/dma-mapping.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/delay.h>
@@ -1229,8 +1230,6 @@ static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	spin_lock_init(&nhi->lock);
 
 	res = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
-	if (res)
-		res = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
 	if (res) {
 		dev_err(&pdev->dev, "failed to set DMA mask\n");
 		return res;