iommu/amd: Use BUG_ON instead of if () BUG()

Found by a coccicheck script.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index a1585796..f82060e7 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1835,8 +1835,8 @@
 		free_gcr3_tbl_level2(domain->gcr3_tbl);
 	else if (domain->glx == 1)
 		free_gcr3_tbl_level1(domain->gcr3_tbl);
-	else if (domain->glx != 0)
-		BUG();
+	else
+		BUG_ON(domain->glx != 0);
 
 	free_page((unsigned long)domain->gcr3_tbl);
 }