iwlwifi: mvm: fix statistics variables type

When receiving statistics notification there is a field of average energy.
This is defines as signed 8 bit, while FW refers to it as unsigned.
when the energy is higher than 127 this causes in iwl_mvm_stat_iterator
a wrong computation of the signal
     int sig = -stats->general.beacon_filter_average_energy;
resulting in incorrect CQM event (change from low to high).

While at it - update the rest of the fields to the correct type.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>