Issues with mt7915 thermal throttling

[Nicolas Cavallari <nicolas.cavallari@green-communications.fr>]

I noticed some strange issues with mt7915's thermal throttling, 
particularly the cooling_device.

First, it seems that the thermal subsystem expect that higher 
cooling_device states provide more cooling, but mt7915e apparently does 
the opposite and use it as a duty cycle, where state=1 does severe 
throttling/max cooling (iperf throughput basically go down to near zero) 
and state=100 is full power.

Also, state=0, from the comments, apparently disable thermal management, 
except that in practice, it does not change the throttle state, since 
throughput stays low when switching from state=1 to state=0, and stays 
high when switching from 100 to 0.

As a result, as soon as the default thermal zone runs a little hot, the 
performance of mt7915e is destroyed and does not recover much when the 
temperature drops down.

I can come up with a patch to fix the first issue, but not the state=0 
one, and i would like some pointers/confirmation.