iwlagn: add temperature offset calib for 6000g2

6000g2 devices need to have temperature offset calibration. The runtime
uCode needs to receive the calibration results just like BB and LO
calibration. To do this, driver reads the offset value from NVM and send
it to uCode after runtime uCode is alive.

Signed-off-by: Shanyu Zhao <shanyu.zhao@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>