ARM: rmobile: Build u-boot-spl.srec on Gen2

The u-boot-spl.srec is needed for the minimon update on Gen2 SoCs,
conveniently generate this file if SPL is enabled.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Cc: Tom Rini <trini@konsulko.com>

include/configs/rcar-gen2-common.h

@@ -15,6 +15,10 @@
 #define CONFIG_SETUP_MEMORY_TAGS
 #define CONFIG_INITRD_TAG
 
+#ifdef CONFIG_SPL
+#define CONFIG_SPL_TARGET	"spl/u-boot-spl.srec"
+#endif
+
 #undef	CONFIG_SHOW_BOOT_PROGRESS
 
 #define CONFIG_ARCH_CPU_INIT