ARM: rmobile: Place initial stack right below U-Boot

Place the stack right below U-Boot so it's not in the way in case
U-Boot grows too much.

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

include/configs/rcar-gen3-common.h

@@ -42,7 +42,7 @@
 
 /* MEMORY */
 #define CONFIG_SYS_TEXT_BASE		0x50000000
-#define CONFIG_SYS_INIT_SP_ADDR		(CONFIG_SYS_TEXT_BASE + 0x7fff0)
+#define CONFIG_SYS_INIT_SP_ADDR		CONFIG_SYS_TEXT_BASE
 
 #define DRAM_RSV_SIZE			0x08000000
 #if defined(CONFIG_R8A7795)