x86, swiotlb: Simplify pci_swiotlb_detect_override()

At the end of the function, the local variable use_swiotlb has always
the same value as the global variable swiotlb. Hence drop the local
variable completely.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

arch/x86/kernel/pci-swiotlb.c

@@ -68,12 +68,10 @@ static struct dma_map_ops swiotlb_dma_ops = {
  */
 int __init pci_swiotlb_detect_override(void)
 {
-	int use_swiotlb = swiotlb | swiotlb_force;
-
 	if (swiotlb_force)
 		swiotlb = 1;
 
-	return use_swiotlb;
+	return swiotlb;
 }
 IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
 		  pci_xen_swiotlb_detect,