serial: s5p: use clock api to get clock rate

On Exynos platforms that support clock driver API, allow the driver to
use clock api get the SCLK clock rate.

Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

drivers/serial/serial_s5p.c

@@ -17,6 +17,7 @@
 #include <asm/arch/clk.h>
 #include <asm/arch/uart.h>
 #include <serial.h>
+#include <clk.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -90,7 +91,19 @@ int s5p_serial_setbrg(struct udevice *dev, int baudrate)
 {
 	struct s5p_serial_platdata *plat = dev->platdata;
 	struct s5p_uart *const uart = plat->reg;
-	u32 uclk = get_uart_clk(plat->port_id);
+	u32 uclk;
+
+#ifdef CONFIG_CLK_EXYNOS
+	struct udevice *clk_dev;
+	u32 ret;
+
+	ret = clk_get_by_index(dev, 1, &clk_dev);
+	if (ret < 0)
+		return ret;
+	uclk = clk_get_periph_rate(clk_dev, ret);
+#else
+	uclk = get_uart_clk(plat->port_id);
+#endif
 
 	s5p_serial_baud(uart, uclk, baudrate);