iommu/mediatek: Make mtk_iommu_pm_ops static

The symbol exists elsewhere already, so that is fails to
link if the symbol is non-static.
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/mtk_iommu_v1.c

@@ -695,7 +695,7 @@ static int __maybe_unused mtk_iommu_resume(struct device *dev)
 	return 0;
 }
 
-const struct dev_pm_ops mtk_iommu_pm_ops = {
+static const struct dev_pm_ops mtk_iommu_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(mtk_iommu_suspend, mtk_iommu_resume)
 };