rk3288: Disable JTAG function from sdmmc0 IO

The GRF_SOC_CON0.grf_force_jtag bit is automatically set at boot and it
is preventing the SDMMC to work correctly. Disable the JTAG function on
the assumption that a working SD has higher priority over JTAG.

Signed-off-by: Carlo Caione <carlo@endlessm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

arch/arm/mach-rockchip/rk3288-board.c

@@ -307,10 +307,10 @@ U_BOOT_CMD(
 	""
 );
 
-#define GRF_SOC_CON2 0xff77024c
-
 int board_early_init_f(void)
 {
+	const uintptr_t GRF_SOC_CON0 = 0xff770244;
+	const uintptr_t GRF_SOC_CON2 = 0xff77024c;
 	struct udevice *pinctrl;
 	struct udevice *dev;
 	int ret;
@@ -339,5 +339,11 @@ int board_early_init_f(void)
 	}
 	rk_setreg(GRF_SOC_CON2, 1 << 0);
 
+	/*
+	 * Disable JTAG on sdmmc0 IO. The SDMMC won't work until this bit is
+	 * cleared
+	 */
+	rk_clrreg(GRF_SOC_CON0, 1 << 12);
+
 	return 0;
 }