sunxi: Use mmc_bootdev=2 for MMC2 boot

With DM_MMC the mmc devices are probed as per dt status
and eMMC can probed maximum device of 2, if all nodes like
mmc0, mmc1 and mmc2 status are 'okay'.

So update mmc_bootdev to 2 and add boot order as 2, 1, 0
devices. so-that it can to boot any identified device even
if the respective device status disabled or unsupported.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>

board/sunxi/board.c

@@ -768,7 +768,7 @@ int misc_init_r(void)
 	} else if (boot == BOOT_DEVICE_MMC1) {
 		env_set("mmc_bootdev", "0");
 	} else if (boot == BOOT_DEVICE_MMC2) {
-		env_set("mmc_bootdev", "1");
+		env_set("mmc_bootdev", "2");
 	}
 
 	setup_environment(gd->fdt_blob);

include/configs/sunxi-common.h

@@ -373,8 +373,10 @@ extern int soft_i2c_gpio_scl;
 #define BOOTENV_DEV_MMC_AUTO(devtypeu, devtypel, instance)		\
 	BOOTENV_DEV_MMC(MMC, mmc, 0)					\
 	BOOTENV_DEV_MMC(MMC, mmc, 1)					\
+	BOOTENV_DEV_MMC(MMC, mmc, 2)					\
 	"bootcmd_mmc_auto="						\
-		"if test ${mmc_bootdev} -eq 1; then "			\
+		"if test ${mmc_bootdev} -eq 2; then "			\
+			"run bootcmd_mmc2; "				\
 			"run bootcmd_mmc1; "				\
 			"run bootcmd_mmc0; "				\
 		"elif test ${mmc_bootdev} -eq 0; then "			\