include: configs: Increase CONFIG_SYS_BOOTM_LEN to 16MB

The default value of CONFIG_SYS_BOOTM_LEN is 0x800000 i.e, 8MB which
causes board reset because of larger uImage size.

This was tested on rk3288 Amarula Vyasa and rk3288 Asus Tinker
boards.

Error log snippet:
   Booting using the fdt blob at 0x1f00000
   Loading Kernel Image ... Image too large: increase CONFIG_SYS_BOOTM_LEN
Must RESET board to recover
resetting ...

Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Shyam Saini <shyam.saini@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/include/configs/rk3288_common.h b/include/configs/rk3288_common.h
index 5472a90..5c3b35c 100644
--- a/include/configs/rk3288_common.h
+++ b/include/configs/rk3288_common.h
@@ -9,6 +9,8 @@
 #include <asm/arch-rockchip/hardware.h>
 #include "rockchip-common.h"
 
+#define CONFIG_SYS_BOOTM_LEN (16 << 20) /* 16MB */
+
 #define CONFIG_SKIP_LOWLEVEL_INIT_ONLY
 #define CONFIG_SYS_MALLOC_LEN		(32 << 20)
 #define CONFIG_SYS_CBSIZE		1024