iwlwifi: dvm: fix chain noise calibration

commit b28b6dfe upstream.

First step of chain noise calibration process had disable flag
check inverted. Chain noise calibration never started because
of this.

Tested on intel 5300 with two antennas attached. The driver
correctly disabled one chain.

Signed-off-by: Nikolay Martynov <mar.kolya@gmail.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>