kernel: don't parse FIT partition on NAND-backed mtdblock

ubiblock devices should be used on NAND flash to store the uImage.FIT
in case the bootloader supports that -- otherwise only rootfs is stored
in UBI while the uImage.FIT contains only the kernel and dtb.
Hence there is no need to enable parsing partitions on NAND mtdblock
devices, it is even responsible for the ugly warning on-opening of the
mtdblock device now. Just don't do it.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

target/linux/generic/hack-5.15/410-block-fit-partition-parser.patch

@@ -112,13 +112,12 @@
  	dev->gd = gd;
 --- a/drivers/mtd/mtd_blkdevs.c
 +++ b/drivers/mtd/mtd_blkdevs.c
-@@ -345,6 +345,9 @@ int add_mtd_blktrans_dev(struct mtd_blkt
+@@ -345,6 +345,8 @@ int add_mtd_blktrans_dev(struct mtd_blkt
  	gd->first_minor = (new->devnum) << tr->part_bits;
  	gd->minors = 1 << tr->part_bits;
  	gd->fops = &mtd_block_ops;
-+#ifdef CONFIG_FIT_PARTITION
-+	gd->flags |= GENHD_FL_EXT_DEVT;
-+#endif
++	if (IS_ENABLED(CONFIG_FIT_PARTITION) && !mtd_type_is_nand(new->mtd))
++		gd->flags |= GENHD_FL_EXT_DEVT;
 
  	if (tr->part_bits)
  		if (new->devnum < 26)