iwlwifi: rate sacaling fixes

1. Fixing support for tx in antenna C
2. Enable stay_in_column expiration after 2 seconds

Signed-off-by: Guy Cohen <guy.cohen@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>