iwlwifi: mvm: set SKIP_OVER_DTIM flag only if needed

setting SKIP_OVER_DTIM when skip_dtim_periods is 0
causes a ucode assert. set the flag only if needed.
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/power.c

@@ -902,9 +902,10 @@ int iwl_mvm_update_d0i3_power_mode(struct iwl_mvm *mvm,
 		if (WARN_ON(!dtimper_msec))
 			return 0;
 
+		cmd.skip_dtim_periods = 300 / dtimper_msec;
+		if (cmd.skip_dtim_periods)
 			cmd.flags |=
 				cpu_to_le16(POWER_FLAGS_SKIP_OVER_DTIM_MSK);
-		cmd.skip_dtim_periods = 300 / dtimper_msec;
 	}
 	iwl_mvm_power_log(mvm, &cmd);
 #ifdef CONFIG_IWLWIFI_DEBUGFS