[FS#146] wndr 3700v4 and 4300v1 couldn't effectively use 128 nand flash space

[LEDE Bugs]

The following task has a new comment added:

FS#146 - wndr 3700v4 and 4300v1 couldn't effectively use 128 nand flash space
User who did this - Arjen de Korte (arjendekorte)

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Better call it WNDR3700_EXPERIMENTAL then, because this patch when applied *will* softbrick a WNDR4300v1 device if you didn't copy the caldata_backup to the new location before.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=146#comment2443