4.9: mtd: kill the nand_ecclayout struct

Regarding these patches "mtd: kill the nand_ecclayout struct" in 4.9:

Anyone aware of an implementation of MTD in 4.9 I might use as template? Any pointers would be appreciated!

I actually found a couple of existing backports in LEDE that might be useful for future use:

1. https://github.com/lede-project/source/tree/master/target/linux/ramips/patches-4.4 (0072-0074)

https://github.com/lede-project/source/blob/master/target/linux/oxnas/patches-4.4/0072-mtd-backport-v4.7-0day-patches-from-Boris.patch

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2.` https://github.com/lede-project/source/tree/master/target/linux/ramips/patches-4.4 (0036 - 0038)"

https://github.com/lede-project/source/blob/master/target/linux/ramips/patches-4.4/0038-mtd-ralink-add-mt7620-nand-driver.patch