nexmon blindness bug (brcmf_cfg80211_nexmon_set_channel)

every once in a while, nexmon dies with:

```
[ 4341.527847] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4101, -110
[ 4344.327806] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4097, -110
[ 4347.127853] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4098, -110
[ 4349.927917] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4099, -110
[ 4352.728074] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4100, -110
[ 4355.527970] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4101, -110
[ 4358.328022] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4102, -110
[ 4361.208095] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4103, -110
[ 4364.008157] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4104, -110
[ 4366.808218] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4105, -110
[ 4369.608431] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4097, -110
[ 4372.408345] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4098, -110
[ 4375.288408] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4099, -110
[ 4378.088474] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4100, -110
[ 4380.891399] brcmfmac: brcmf_cfg80211_nexmon_set_channel: Set Channel failed: chspec=4101, -110
```

And only a reboot can fix the wifi, this is why the `mon_max_blind_epochs` parameter exists, to reboot the board when this happens.

Ideally we should document this known issue, the configuration and some day maybe fix it.