iwlagn: re-enable calibration

During the RXON rewrite, this code got lost.
When we've just associated, we need to enable
all calibrations and see if some were already
finished. Add back the missing code.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>