rockchip: rk3368: use defaule value for SYS_MALLOC_F_LEN

There is no difference in rk3368 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/rk3368/Kconfig b/arch/arm/mach-rockchip/rk3368/Kconfig
index 141d2f6..2220f59 100644
--- a/arch/arm/mach-rockchip/rk3368/Kconfig
+++ b/arch/arm/mach-rockchip/rk3368/Kconfig
@@ -48,6 +48,9 @@
 config SYS_SOC
 	default "rk3368"
 
+config SYS_MALLOC_F_LEN
+	default 0x2000
+
 source "board/theobroma-systems/lion_rk3368/Kconfig"
 source "board/rockchip/sheep_rk3368/Kconfig"
 source "board/geekbuying/geekbox/Kconfig"