phy: phy-mtk-tphy: remove the check of -ENOSYS

No need check -ENOSYS anymore after add dummy_enable() for
fixed-clock.

Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/phy/phy-mtk-tphy.c b/drivers/phy/phy-mtk-tphy.c
index 3701481..c4fb404 100644
--- a/drivers/phy/phy-mtk-tphy.c
+++ b/drivers/phy/phy-mtk-tphy.c
@@ -204,9 +204,8 @@
 	struct mtk_phy_instance *instance = tphy->phys[phy->id];
 	int ret;
 
-	/* we may use a fixed-clock here */
 	ret = clk_enable(&instance->ref_clk);
-	if (ret && ret != -ENOSYS)
+	if (ret)
 		return ret;
 
 	switch (instance->type) {