ALSA: emu10k1: Stop using iommu_present()

iommu_get_domain_for_dev() is already perfectly happy to return NULL
if the given device has no IOMMU. Drop the unnecessary check in favour
of just handling that condition appropriately.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/9b506b4a4fe8a7f40aa8bad1aafc82426cf3dd92.1649165210.git.robin.murphy@arm.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/emu10k1/emu10k1_main.c

@@ -1751,11 +1751,8 @@ static void snd_emu10k1_detect_iommu(struct snd_emu10k1 *emu)
 
 	emu->iommu_workaround = false;
 
-	if (!iommu_present(emu->card->dev->bus))
-		return;
-
 	domain = iommu_get_domain_for_dev(emu->card->dev);
-	if (domain && domain->type == IOMMU_DOMAIN_IDENTITY)
+	if (!domain || domain->type == IOMMU_DOMAIN_IDENTITY)
 		return;
 
 	dev_notice(emu->card->dev,