iwlwifi: mvm: remove support for legacy power API

If the driver detects old firmware, we disable support for
power management.
This greatly simplifies the code.

Reviewed-by: Alexander Bondar <alexander.bondar@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/mvm/debugfs.c b/drivers/net/wireless/iwlwifi/mvm/debugfs.c
index c116765..6853e5e 100644
--- a/drivers/net/wireless/iwlwifi/mvm/debugfs.c
+++ b/drivers/net/wireless/iwlwifi/mvm/debugfs.c
@@ -250,7 +250,7 @@
 	}
 
 	mutex_lock(&mvm->mutex);
-	ret = iwl_mvm_power_update_device_mode(mvm);
+	ret = iwl_mvm_power_update_device(mvm);
 	mutex_unlock(&mvm->mutex);
 
 	return ret ?: count;