sunxi: Remove the MMC index hack

The current code, if there's both an eMMC and an MMC slot available on the
board, will swap the MMC indices based on whether we booted from the eMMC
or the MMC. This way, the MMC we're supposed to boot on will always have
the index 0.

However, this causes various issues, for example when using other
components that base their behaviour on the MMC index, such as fastboot.

Let's remove that hack, and take the opposite approach. The MMC will always
have the same index, but the bootcmd will pick the same device than the one
we booted from. This is done through the introduction of the mmc_bootdev
environment variable that will be filled by the board code based on the
boot device informations we can get from the SoC.

In order to not introduce regressions, we also need to adjust the fastboot
MMC device and the environment device in order to set it to the eMMC, over
the MMC, like it used to be the case.

Tested-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/board/sunxi/board.c b/board/sunxi/board.c
index 7fdcc4a..cb42742 100644
--- a/board/sunxi/board.c
+++ b/board/sunxi/board.c
@@ -492,20 +492,6 @@
 		return -1;
 #endif
 
-#if !defined(CONFIG_SPL_BUILD) && CONFIG_MMC_SUNXI_SLOT_EXTRA == 2
-	/*
-	 * On systems with an emmc (mmc2), figure out if we are booting from
-	 * the emmc and if we are make it "mmc dev 0" so that boot.scr, etc.
-	 * are searched there first. Note we only do this for u-boot proper,
-	 * not for the SPL, see spl_boot_device().
-	 */
-	if (readb(SPL_ADDR + 0x28) == SUNXI_BOOTED_FROM_MMC2) {
-		/* Booting from emmc / mmc2, swap */
-		mmc0->block_dev.devnum = 1;
-		mmc1->block_dev.devnum = 0;
-	}
-#endif
-
 	return 0;
 }
 #endif
@@ -725,12 +711,18 @@
 
 	env_set("fel_booted", NULL);
 	env_set("fel_scriptaddr", NULL);
+	env_set("mmc_bootdev", NULL);
 
 	boot = sunxi_get_boot_device();
 	/* determine if we are running in FEL mode */
 	if (boot == BOOT_DEVICE_BOARD) {
 		env_set("fel_booted", "1");
 		parse_spl_header(SPL_ADDR);
+	/* or if we booted from MMC, and which one */
+	} else if (boot == BOOT_DEVICE_MMC1) {
+		env_set("mmc_bootdev", "0");
+	} else if (boot == BOOT_DEVICE_MMC2) {
+		env_set("mmc_bootdev", "1");
 	}
 
 	setup_environment(gd->fdt_blob);