hwmon: (lm90) Support temp_samples attribute

Several of the chips supported by this driver support configuring the
number of samples (or the fault queue depth) necessary before a fault
or alarm is reported. This is done either with a bit in the configuration
register or with a separate "consecutive alert" register. Support this
functionality with the temp_samples attribute.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>