serial: zynq: Initialize uart only before relocation

This issue was found when OF_LIVE was enabled that there are scrambled
chars on the console like this:
Chip ID:	zu3eg
Watchdog: Started��j�   sdhci@ff160000: 0, sdhci@ff170000: 1
In:    serial@ff010000

I found a solution for this problem exactly the same as I found later in
serial_msm fixed by:
"serial: serial_msm: initialize uart only before relocation"
(sha1: 7e5ad796bc)

What it is happening is that output TX fifo still contains chars to be
sent and _uart_zynq_serial_init() resets TX fifo even in the middle of
transfer.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/serial/serial_zynq.c

@@ -15,6 +15,8 @@
 #include <linux/compiler.h>
 #include <serial.h>
 
+DECLARE_GLOBAL_DATA_PTR;
+
 #define ZYNQ_UART_SR_TXACTIVE	BIT(11) /* TX active */
 #define ZYNQ_UART_SR_TXFULL	BIT(4) /* TX FIFO full */
 #define ZYNQ_UART_SR_RXEMPTY	BIT(1) /* RX FIFO empty */
@@ -137,6 +139,10 @@ static int zynq_serial_probe(struct udevice *dev)
 {
 	struct zynq_uart_priv *priv = dev_get_priv(dev);
 
+	/* No need to reinitialize the UART after relocation */
+	if (gd->flags & GD_FLG_RELOC)
+		return 0;
+
 	_uart_zynq_serial_init(priv->regs);
 
 	return 0;