uboot-imx6: fall back to MMC for SPL if boot mode is invalid

Fixes boot on Hummingboard

Signed-off-by: Felix Fietkau <nbd@nbd.name>

package/boot/uboot-imx6/patches/110-mx6cuboxi-mmc-fallback.patch

@@ -0,0 +1,26 @@
+--- a/board/solidrun/mx6cuboxi/mx6cuboxi.c
++++ b/board/solidrun/mx6cuboxi/mx6cuboxi.c
+@@ -334,6 +334,12 @@ int board_init(void)
+ 	return ret;
+ }
+ 
++void board_boot_order(u32 *spl_boot_list)
++{
++	spl_boot_list[0] = spl_boot_device();
++	spl_boot_list[1] = BOOT_DEVICE_MMC1;
++}
++
+ static bool is_hummingboard(void)
+ {
+ 	int val1, val2;
+--- a/arch/arm/mach-imx/spl.c
++++ b/arch/arm/mach-imx/spl.c
+@@ -136,7 +136,7 @@ int g_dnl_bind_fixup(struct usb_device_d
+ /* called from spl_mmc to see type of boot mode for storage (RAW or FAT) */
+ u32 spl_boot_mode(const u32 boot_device)
+ {
+-	switch (spl_boot_device()) {
++	switch (boot_device) {
+ 	/* for MMC return either RAW or FAT mode */
+ 	case BOOT_DEVICE_MMC1:
+ 	case BOOT_DEVICE_MMC2: