rockchip: add option to change method of loading u-boot

If we would like to boot from SD card, we have to implement mmc driver
in SPL stage, and get a slightly large SPL binary. Rockchip SoC's
bootrom code has the ability to load spl and u-boot, then boot.

If CONFIG_ROCKCHIP_SPL_BACK_TO_BROM is enabled, the spl will return to
bootrom in board_init_f(), then bootrom loads u-boot binary.

Loading sequence after rework:
bootrom ==> spl ==> bootrom ==> u-boot

Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>
Fixed up spelling of U-Boot, boorom, opinion->option, Rochchip:
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-rockchip/Makefile b/arch/arm/mach-rockchip/Makefile
index 55567cb..c08d61b 100644
--- a/arch/arm/mach-rockchip/Makefile
+++ b/arch/arm/mach-rockchip/Makefile
@@ -7,6 +7,7 @@
 ifdef CONFIG_SPL_BUILD
 obj-$(CONFIG_ROCKCHIP_RK3288) += rk3288-board-spl.o
 obj-$(CONFIG_ROCKCHIP_RK3036) += rk3036-board-spl.o
+obj-$(CONFIG_ROCKCHIP_SPL_BACK_TO_BROM) += save_boot_param.o
 else
 obj-$(CONFIG_ROCKCHIP_RK3288) += board.o
 endif