kernel: fix mtd squashfs root regression on targets with CONFIG_FIT_PARTITION

Move 480-mtd-set-rootfs-to-be-root-dev.patch to hack-5.10 and fix assumption
about the block device index.

Fixes: 2809d00007 ("kernel: support FIT partition parser on mtdblock devices")
Acked-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/linux/generic/pending-5.10/480-mtd-set-rootfs-to-be-root-dev.patch

@@ -1,38 +0,0 @@
-From: Gabor Juhos <juhosg@openwrt.org>
-Subject: kernel/3.1[02]: move MTD root device setup code to mtdcore
-
-The current code only allows to automatically set
-root device on MTD partitions. Move the code to MTD
-core to allow to use it with all MTD devices.
-
-Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
----
- drivers/mtd/mtdcore.c | 10 ++++++++++
- 1 file changed, 10 insertions(+)
-
---- a/drivers/mtd/mtdcore.c
-+++ b/drivers/mtd/mtdcore.c
-@@ -27,6 +27,7 @@
- #include <linux/reboot.h>
- #include <linux/leds.h>
- #include <linux/debugfs.h>
-+#include <linux/root_dev.h>
- #include <linux/nvmem-provider.h>
- 
- #include <linux/mtd/mtd.h>
-@@ -693,6 +694,15 @@ int add_mtd_device(struct mtd_info *mtd)
- 	   of this try_ nonsense, and no bitching about it
- 	   either. :) */
- 	__module_get(THIS_MODULE);
-+
-+	if (!strcmp(mtd->name, "rootfs") &&
-+	    IS_ENABLED(CONFIG_MTD_ROOTFS_ROOT_DEV) &&
-+	    ROOT_DEV == 0) {
-+		pr_notice("mtd: device %d (%s) set to be root filesystem\n",
-+			  mtd->index, mtd->name);
-+		ROOT_DEV = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
-+	}
-+
- 	return 0;
- 
- fail_nvmem_add:

target/linux/generic/pending-5.10/495-mtd-core-add-get_mtd_device_by_node.patch

@@ -17,7 +17,7 @@ Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
 
 --- a/drivers/mtd/mtdcore.c
 +++ b/drivers/mtd/mtdcore.c
-@@ -1053,6 +1053,44 @@ out_unlock:
+@@ -1043,6 +1043,44 @@ out_unlock:
  }
  EXPORT_SYMBOL_GPL(get_mtd_device_nm);