rockchip: rk3188: rock: adjust for SPL/TPL split

With the changes to split SPL/TPL for the RK3368, I apparently missed
some needed adjustments to the RK3188 Kconfig and rock_defconfig.

This fixes build-issues for the rock board after applying the RK3368
enablement (and SPL/TPL) set that resulted from TPL_SERIAL_SUPPORT,
TPL_ROCKCHIP_BACK_TO_BROM and TPL_TINY_MEMSET being separate symbols
now.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-rockchip/Makefile b/arch/arm/mach-rockchip/Makefile
index c3ed862..79e9704 100644
--- a/arch/arm/mach-rockchip/Makefile
+++ b/arch/arm/mach-rockchip/Makefile
@@ -35,7 +35,9 @@
 endif
 
 obj-$(CONFIG_ROCKCHIP_RK3036) += rk3036/
-obj-tpl-$(CONFIG_ROCKCHIP_RK3188) += rk3188/
+ifndef CONFIG_TPL_BUILD
+obj-$(CONFIG_ROCKCHIP_RK3188) += rk3188/
+endif
 obj-$(CONFIG_ROCKCHIP_RK322X) += rk322x/
 obj-$(CONFIG_ROCKCHIP_RK3288) += rk3288/
 obj-$(CONFIG_ROCKCHIP_RK3328) += rk3328/