kernel: copy kernel 4.19 code to 5.4

No changes were done to the patches while coping them. Currently they do
not apply on top of kernel 5.4.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/generic/pending-5.4/480-mtd-set-rootfs-to-be-root-dev.patch

@@ -0,0 +1,38 @@
+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
+@@ -41,6 +41,7 @@
+ #include <linux/reboot.h>
+ #include <linux/leds.h>
+ #include <linux/debugfs.h>
++#include <linux/root_dev.h>
+ 
+ #include <linux/mtd/mtd.h>
+ #include <linux/mtd/partitions.h>
+@@ -593,6 +594,15 @@ 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_added: