Verify txpower option is working on Picostation

[westbywest]

Observation from IS4CWN suggests that Picostation M2 nodes seem to have their txpower fixed at 16dmb / 39mW. This is despite seeing different values set explicitly in /etc/config/wireless, and it's been observed consistently enough to rule the possibility that nodes are simply retaining a txpower setting that was previously set via command line and not rebooted. Likewise, I can confirm the ability to set different txpower settings on Nanonstation Loco M2 APs using another OpenWRT AA derivative of nearly identical vintage, indicating an issue specific to Picostations.

I'm filing this issue so that it doesn't get forgotten, and in case this becomes an issue to file upstream.

[areynold]

iw wlan0 set txpower fixed [100-10000] seems to work, but uci set wireless.radio0.txpower=[1-17]; uci commit does not seem to change anything. Entirely possible that my syntax or range is wrong.

[areynold]

Oops. uci commands work if you restart networking after you commit.

txpower works with values 0-16. I saw transmit values of roughly -35dbm for 0 and -2dbm for 16. @hawkinswnaf has confirmed that he regularly sets txpower values to get proper network topology at the lab testbed.