board: am335x: Allow to choose serial device dynamically

Different AM335x based platforms have different serial consoles. As serial
console is Kconfig option a separate defconfig has to be created for each
platform. So pass the serial device dynamically.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/board/ti/am335x/board.c b/board/ti/am335x/board.c
index ff52314..56f4984 100644
--- a/board/ti/am335x/board.c
+++ b/board/ti/am335x/board.c
@@ -11,6 +11,7 @@
 #include <common.h>
 #include <errno.h>
 #include <spl.h>
+#include <serial.h>
 #include <asm/arch/cpu.h>
 #include <asm/arch/hardware.h>
 #include <asm/arch/omap.h>
@@ -59,6 +60,16 @@
 	return ti_i2c_eeprom_am_get(-1, CONFIG_SYS_I2C_EEPROM_ADDR);
 }
 
+#ifndef CONFIG_DM_SERIAL
+struct serial_device *default_serial_console(void)
+{
+	if (board_is_icev2())
+		return &eserial4_device;
+	else
+		return &eserial1_device;
+}
+#endif
+
 #ifndef CONFIG_SKIP_LOWLEVEL_INIT
 static const struct ddr_data ddr2_data = {
 	.datardsratio0 = MT47H128M16RT25E_RD_DQS,