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/board.c b/arch/arm/mach-rockchip/board.c
index 816540e..b07e073 100644
--- a/arch/arm/mach-rockchip/board.c
+++ b/arch/arm/mach-rockchip/board.c
@@ -10,12 +10,45 @@
 #include <ram.h>
 #include <asm/io.h>
 #include <asm/arch/clock.h>
+#include <asm/arch/periph.h>
+#include <asm/gpio.h>
+#include <dm/pinctrl.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
 int board_init(void)
 {
+#ifdef CONFIG_ROCKCHIP_SPL_BACK_TO_BROM
+	struct udevice *pinctrl;
+	int ret;
+
+    /*
+     * We need to implement sdcard iomux here for the further
+     * initlization, otherwise, it'll hit sdcard command sending
+     * timeout exception.
+     */
+	ret = uclass_get_device(UCLASS_PINCTRL, 0, &pinctrl);
+	if (ret) {
+		debug("%s: Cannot find pinctrl device\n", __func__);
+		goto err;
+	}
+	ret = pinctrl_request_noflags(pinctrl, PERIPH_ID_SDCARD);
+	if (ret) {
+		debug("%s: Failed to set up SD card\n", __func__);
+		goto err;
+	}
+
+	return 0;
+err:
+	printf("board_init: Error %d\n", ret);
+
+	/* No way to report error here */
+	hang();
+
+	return -1;
+#else
 	return 0;
+#endif
 }
 
 int dram_init(void)