[FS#863] ath9k failure with AP+11s VIFs ("unsupported hw bitrate detected")

[LEDE Bugs]

The following task has a new comment added:

FS#863 - ath9k failure with AP+11s VIFs ("unsupported hw bitrate detected")
User who did this - Marcus Scharf (Sunz3r)

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https://pastebin.com/n8zgqB7E

"iw dev client0 scan" bring the node back despite this error

Software: Gluon v2016.2.5
Hardware: WR841v10
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=863#comment2852