iwlwifi: stop dbgc recording before stopping DMA

Today we stop the device and the DMA without stopping the dbgc
recording before. This causes host crashes when the DMA
rate is high.

Stop dbgc recording when clearing the fw debug configuration
to fix this.

Signed-off-by: Golan Ben Ami <golan.ben.ami@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>