IOMMU-API: use ANSI style function declaration for 'iommu_found'

Fix this sparse warning:
  drivers/base/iommu.c:34:18: warning: non-ANSI function declaration of function 'iommu_found'
Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

drivers/base/iommu.c

@@ -31,7 +31,7 @@ void register_iommu(struct iommu_ops *ops)
 	iommu_ops = ops;
 }
 
-bool iommu_found()
+bool iommu_found(void)
 {
 	return iommu_ops != NULL;
 }