[U-Boot] rockchip: update ROCKCHIP_SPL_RESERVE_IRAM to 0

[Philipp Tomsich]

> Only rk3399 atf need ROCKCHIP_SPL_RESERVE_IRAM, so update it dtfault
> 0 so that other SoCs do not need to define it.
> 
> Signed-off-by: Kever Yang <kever.yang at rock-chips.com>
> ---
> 
>  arch/arm/mach-rockchip/Kconfig   | 2 +-
>  configs/evb-rk3399_defconfig     | 1 +
>  configs/firefly-rk3399_defconfig | 1 +
>  3 files changed, 3 insertions(+), 1 deletion(-)
> 

Acked-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>