serial: imx: add clk_prepare/clk_unprepare

It's for migrating to generic clk framework API.
Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

drivers/tty/serial/imx.c

@@ -1508,7 +1508,7 @@ static int serial_imx_probe(struct platform_device *pdev)
 		ret = PTR_ERR(sport->clk);
 		goto unmap;
 	}
-	clk_enable(sport->clk);
+	clk_prepare_enable(sport->clk);
 
 	sport->port.uartclk = clk_get_rate(sport->clk);
 
@@ -1531,8 +1531,8 @@ static int serial_imx_probe(struct platform_device *pdev)
 	if (pdata && pdata->exit)
 		pdata->exit(pdev);
 clkput:
+	clk_disable_unprepare(sport->clk);
 	clk_put(sport->clk);
-	clk_disable(sport->clk);
 unmap:
 	iounmap(sport->port.membase);
 free:
@@ -1552,11 +1552,10 @@ static int serial_imx_remove(struct platform_device *pdev)
 
 	if (sport) {
 		uart_remove_one_port(&imx_reg, &sport->port);
+		clk_disable_unprepare(sport->clk);
 		clk_put(sport->clk);
 	}
 
-	clk_disable(sport->clk);
-
 	if (pdata && pdata->exit)
 		pdata->exit(pdev);