iwlwifi: modify sensitivity value for 5150

In 5150 there is a long delay between the AGC(Automatic Gain Control) command
till the RF is stabilized causing us to miss detections when there was
adjacent channel noise, so we need to adjusted the Sensitivity calibration
for 5150 differently.

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>