[FS#1376] regression: reading from 32 MB flash mtd fails with kernel 4.9

[LEDE Bugs]

The following task has a new comment added:

FS#1376 - regression: reading from 32 MB flash mtd fails with kernel 4.9
User who did this - Christian Beier (bk138)

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Commenting out 

if (msg->addr_width > 3)
     return -EOPNOTSUPP;

in ath79_spi_read_flash_data() in drivers/spi/spi-ath79.c makes the boxx boot, but hard crash soon afterwards and then reboot. Seems this is in there for a reason.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1376#comment4364