hwmon: Add support for power min, lcrit, min_alarm and lcrit_alarm

Some sensors support reporting minimal and lower critical power, as
well as alarms when these thresholds are reached. Add support for
these attributes to the hwmon core.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>