sh4: use single u-boot linker script for all boards

Three supported SH4/SH4A boards with the bootloader image stored on
SPI flash have own flavour of a linker script, in turn they are equal
among each other. The only difference is that the text from
lowlevel_init.o is placed right after start.o, which makes sense.

Note that .bss section is not marked as NOLOAD, because for about
10 years this is a default option of a GNU linker, either the
attribute is found or not the resulting image file is the same.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sh/cpu/u-boot.lds

@@ -11,6 +11,8 @@
  * SPDX-License-Identifier:	GPL-2.0+
  */
 
+#include "config.h"
+
 OUTPUT_FORMAT("elf32-sh-linux", "elf32-sh-linux", "elf32-sh-linux")
 OUTPUT_ARCH(sh)
 ENTRY(_start)
@@ -29,6 +31,8 @@ SECTIONS
 	.text :
 	{
 		KEEP(*/start.o		(.text))
+		KEEP(CONFIG_BOARDDIR/lowlevel_init.o	(.spiboot1.text))
+		KEEP(*(.spiboot2.text))
 		. = ALIGN(8192);
 		common/env_embedded.o	(.ppcenv)
 		. = ALIGN(8192);