ramips: limit 5GHz channels for RAVPower RP-WD009
When selecting a channel below 100 on the 5GHz radio, the channel will
be detected as busy all the time.
Survey data from wlan1
frequency: 5240 MHz [in use]
channel active time: 165729 ms
channel busy time: 158704 ms
channel transmit time: 0 ms
Channels 100 and above work fine:
Survey data from wlan1
frequency: 5500 MHz
channel active time: 133000 ms
channel busy time: 21090 ms
channel transmit time: 0 ms
Limit the available channels, so users do not have the impression
their device is broken.
Signed-off-by: David Bauer <mail@david-bauer.net>