[Nouveau] hwmon API update

[Martin Peres]

Hi,

I am working on power management on the nouveau driver and I need a way 
to get data out of and send commands to the i2c drivers from the kernel 
space.

We can already change the clocks of the card, but we need a way to 
monitor the temperature and bump the fan speed if needed.
Another problem with letting users mess with the i2c driver by 
themselves is that some cards use the i2c driver for fan management 
while others don't. This is why I would like to introduce nouveau as an 
hwmon driver, exporting the temperature, fan management and clock speeds 
so as we can use the thermal zone to monitor the temperature and react 
when needed.

So far, we use:
- w83l785ts
- w83781d
- adt7473 (most common one)
- f75375
- lm99

With the help of Matthew Garret, I updated his previous proposal for an 
in-kernel API for hwmon. The patch should apply cleanly on Linux 
2.6.38-rc4. This patch only provides the API, no modification to the 
drivers has been completed yet.

Looking forward to your review and feedback.

Martin