ARM: rmobile: Zap checkboard on Gen3

The checkboard() function showing hard-coded board model for which the
U-Boot was built is superseded on Gen3 by show_board_info() displaying
the Model from device tree. Add small ifdef to stop compiling the
function into U-Boot.

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

arch/arm/mach-rmobile/board.c

@@ -8,8 +8,10 @@
 #include <asm/io.h>
 #include <asm/arch/sys_proto.h>
 
+#ifndef CONFIG_RCAR_GEN3
 int checkboard(void)
 {
 	printf("Board: %s\n", sysinfo.board_string);
 	return 0;
 }
+#endif