iwlwifi: mvm: disable completely low latency mode with debugfs

We introduce a new state for latency, force mode, in force mode
you can enable always to be in low latency or always to be in non
low latency.

This is required for test mode in max TpT test.

Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>