iwlwifi: mvm: refactor power code

The main complexity of the power code is that it needs to
take into account the firmware limitations.
These limitations state that we need to have a global
picture of the vifs present in the system to be able to
decide if we can enable power management on a specific vif.

Even device power save (as opposed to vif power management)
must be disabled in certain circumstances (monitor vif).

Refactor the current code to make this clearer by defining
a function that explicitely computes these constraints.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/debugfs-vif.c

@@ -185,7 +185,7 @@ static ssize_t iwl_dbgfs_pm_params_write(struct ieee80211_vif *vif, char *buf,
 
 	mutex_lock(&mvm->mutex);
 	iwl_dbgfs_update_pm(mvm, vif, param, val);
-	ret = iwl_mvm_power_mac_update_mode(mvm, vif);
+	ret = iwl_mvm_power_update_mac(mvm, vif);
 	mutex_unlock(&mvm->mutex);
 
 	return ret ?: count;