rockchip: rk3399: use default value for SYS_MALLOC_F_LEN

There is no difference in rk3399 board use for SYS_MALLOC_F_LEN,
so we can use default value.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/rk3399/Kconfig b/arch/arm/mach-rockchip/rk3399/Kconfig
index f582577..799b326 100644
--- a/arch/arm/mach-rockchip/rk3399/Kconfig
+++ b/arch/arm/mach-rockchip/rk3399/Kconfig
@@ -71,7 +71,7 @@
 	default "rk3399"
 
 config SYS_MALLOC_F_LEN
-	default 0x0800
+	default 0x4000
 
 config TPL_LDSCRIPT
 	default "arch/arm/mach-rockchip/u-boot-tpl-v8.lds"