From: Felix Fietkau <nbd@nbd.name>
Date: Sat Apr 10 17:00:57 2021 +0200
Subject: [PATCH] mtd: fix squashfs root on targets with CONFIG_FIT_PARTITION

Fix assumption about the block device index
---

--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -767,6 +767,9 @@ int add_mtd_device(struct mtd_info *mtd)
 		unsigned int index = mtd->index;
 		pr_notice("mtd: device %d (%s) set to be root filesystem\n",
 			  mtd->index, mtd->name);
+#ifdef CONFIG_FIT_PARTITION
+		index <<= 2;
+#endif
 		ROOT_DEV = MKDEV(MTD_BLOCK_MAJOR, index);
 	}