rockchip: config: tiner-rk3288: extend CONFIG_SYS_MONITOR_LEN to 600KB

The raw u-boot.bin for tinker board has been about 450KB without
debug option, and 550KB with all debug on, and the default value is 200KB,
which is not enough for run raw u-boot.bin.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/include/configs/tinker_rk3288.h b/include/configs/tinker_rk3288.h
index 5adae68..32057b3 100644
--- a/include/configs/tinker_rk3288.h
+++ b/include/configs/tinker_rk3288.h
@@ -18,5 +18,6 @@
 	func(DHCP, dchp, na)
 
 #define CONFIG_SYS_MMC_ENV_DEV 1
+#define CONFIG_SYS_MONITOR_LEN (600 * 1024)
 
 #endif