iwlwifi: Temperature sensor voltage reading for 5150

iwlwifi: Temperature sensor voltage reading for 5150

The temperature measurement by uCode for 5150 and 5000 are different
        CSR_HW_REV_TYPE_5150: temperature sensor output voltage
        CSR_HW_REV_TYPE_5000: temperature in Celsius
temperature related operation for 5150 is measured by temperature sensor
output voltage; additional conversion is required for set and store
the temperature.

To make sure support different HW design; implement _ops method for
temperature related functions (temperature reading and set ct kill
threshold)

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>