iwlwifi: additional items in sensitivity range table

Add more items to sensitivity range table to avoid using hardcoded values.
Initialize the table per device since unique per device information is
required to perform sensitivity calibration.

additional items in sensitivity range table:
   .barker_corr_th_min: Barker correlation threshold minimum
   .barker_corr_th_min_mrc: Barker correlation threshold minimum for MRC
   .nrg_th_cca: Energy threshold for Clear Channel Assessment

Barker codes are a technique used in WLAN encoding for transmission.
MRC is "Maximal Ratio Combining", a technique for optimally combining the
signals from 2 or more receivers to achieve a better signal.

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>