serial: sc16is7xx: Use devm_clk_get_optional()

Replace open coded variants of devm_clk_get_optional().

Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/sc16is7xx.c

···
 	/* Always ask for fixed clock rate from a property. */
 	device_property_read_u32(dev, "clock-frequency", &uartclk);
 
-	s->clk = devm_clk_get(dev, NULL);
-	if (IS_ERR(s->clk)) {
+	s->clk = devm_clk_get_optional(dev, NULL);
+	if (IS_ERR(s->clk))
+		return PTR_ERR(s->clk);
+
+	ret = clk_prepare_enable(s->clk);
+	if (ret)
+		return ret;
+
+	freq = clk_get_rate(s->clk);
+	if (freq == 0) {
 		if (uartclk)
 			freq = uartclk;
 		if (pfreq)
···
 		if (freq)
 			dev_dbg(dev, "Clock frequency: %luHz\n", freq);
 		else
-			return PTR_ERR(s->clk);
-	} else {
-		ret = clk_prepare_enable(s->clk);
-		if (ret)
-			return ret;
-
-		freq = clk_get_rate(s->clk);
+			return -EINVAL;
 	}
 
 	s->regmap = regmap;
···
 	kthread_stop(s->kworker_task);
 
 out_clk:
-	if (!IS_ERR(s->clk))
-		clk_disable_unprepare(s->clk);
+	clk_disable_unprepare(s->clk);
 
 	return ret;
 }
···
 	kthread_flush_worker(&s->kworker);
 	kthread_stop(s->kworker_task);
 
-	if (!IS_ERR(s->clk))
-		clk_disable_unprepare(s->clk);
+	clk_disable_unprepare(s->clk);
 
 	return 0;
 }