rockchip: rk3288: include header for back_to_bootrom

To avoid a warning, we need to include the header defining
back_to_bootrom for us.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/arch/arm/mach-rockchip/rk3288-board-tpl.c b/arch/arm/mach-rockchip/rk3288-board-tpl.c
index a984806..787129b 100644
--- a/arch/arm/mach-rockchip/rk3288-board-tpl.c
+++ b/arch/arm/mach-rockchip/rk3288-board-tpl.c
@@ -10,6 +10,7 @@
 #include <spl.h>
 #include <version.h>
 #include <asm/io.h>
+#include <asm/arch-rockchip/bootrom.h>
 #include <asm/arch-rockchip/clock.h>
 #include <asm/arch-rockchip/sys_proto.h>
 #include <asm/arch-rockchip/timer.h>