swiotlb: remove swiotlb_nr_tbl

All callers just use it to check if swiotlb is active at all, for which
they can just use is_swiotlb_active.  In the longer run drivers need
to stop using is_swiotlb_active as well, but let's do the simple step
first.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index 2d75026..b7a8f3a 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -693,7 +693,7 @@ static int pcifront_connect_and_init_dma(struct pcifront_device *pdev)
 
 	spin_unlock(&pcifront_dev_lock);
 
-	if (!err && !swiotlb_nr_tbl()) {
+	if (!err && !is_swiotlb_active()) {
 		err = pci_xen_swiotlb_init_late();
 		if (err)
 			dev_err(&pdev->xdev->dev, "Could not setup SWIOTLB!\n");