rockchip: Fix u-boot-rockchip.bin build

Currently there are a few arm32 rockchip board configs that don't
generate u-boot-rockchip.bin when running make because CONFIG_BINMAN
is not enabled. This patch changes CONFIG_ARCH_ROCKCHIP to also select
CONFIG_BINMAN if CONFIG_SPL and !CONFIG_ARM64.

Example builds that don't generate u-boot-rockchip.bin without this
patch:

export ARCH=arm
export CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf-
make kylin-rk3036_defconfig
make

export ARCH=arm
export CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf-
make rock_defconfig
make

export ARCH=arm
export CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf-
make tinker-rk3288_defconfig
make

Signed-off-by: Johan Gunnarsson <johan.gunnarsson@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>