iwlwifi: removes the RUN_TIME_CALIB ifdef

This patch removes the possibility not to compile the run time
calibrations. It also renames priv->sensitivity_work to
priv->run_time_calib_work, and moves bg_run_time_calib to iwl4965_base
since it is common to both: 4965 and 5000.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>