tegra: spl: Enable debug UART

Enable the debug UART in SPL to allow early serial output even if the
standard UART does not work (e.g. due to driver model problem).

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Tested-on: Beaver, Jetson-TK1
Tested-by: Stephen Warren <swarren@nvidia.com>

arch/arm/mach-tegra/spl.c

@@ -7,6 +7,7 @@
  * SPDX-License-Identifier:	GPL-2.0+
  */
 #include <common.h>
+#include <debug_uart.h>
 #include <spl.h>
 
 #include <asm/io.h>
@@ -32,6 +33,9 @@ void spl_board_init(void)
 	gpio_early_init_uart();
 
 	clock_early_init();
+#ifdef CONFIG_DEBUG_UART
+	debug_uart_init();
+#endif
 	preloader_console_init();
 }