iwlwifi: mld: fix building with CONFIG_PM_SLEEP disabled

The newly added driver causes multiple build problems when CONFIG_PM_SLEEP is
disabled:

drivers/net/wireless/intel/iwlwifi/mld/mac80211.c:1982:12: error: 'iwl_mld_resume' defined but not used [-Werror=unused-function]
 1982 | static int iwl_mld_resume(struct ieee80211_hw *hw)
      |            ^~~~~~~~~~~~~~
drivers/net/wireless/intel/iwlwifi/mld/mac80211.c:1960:1: error: 'iwl_mld_suspend' defined but not used [-Werror=unused-function]
 1960 | iwl_mld_suspend(struct ieee80211_hw *hw, struct cfg80211_wowlan *wowlan)
      | ^~~~~~~~~~~~~~~
drivers/net/wireless/intel/iwlwifi/mld/mac80211.c:1946:13: error: 'iwl_mld_set_wakeup' defined but not used [-Werror=unused-function]
 1946 | static void iwl_mld_set_wakeup(struct ieee80211_hw *hw, bool enabled)
      |             ^~~~~~~~~~~~~~~~~~
drivers/net/wireless/intel/iwlwifi/mld/mac80211.c: In function 'iwl_mld_mac80211_start':
drivers/net/wireless/intel/iwlwifi/mld/mac80211.c:504:20: error: 'ret' is used uninitialized [-Werror=uninitialized]
  504 |         if (!in_d3 || ret) {
      |                    ^~
drivers/net/wireless/intel/iwlwifi/mld/mac80211.c:478:13: note: 'ret' was declared here
  478 |         int ret;
      |             ^~~

Hide the unused functions and make sure the 'ret' variable is not used
before the initialization.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20250325084340.378724-1-arnd@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/mld/mac80211.c

@@ -501,7 +501,7 @@ int iwl_mld_mac80211_start(struct ieee80211_hw *hw)
 		iwl_mld_restart_cleanup(mld);
 	}
 
-	if (!in_d3 || ret) {
+	if (!in_d3) {
 		ret = iwl_mld_start_fw(mld);
 		if (ret)
 			goto error;
@@ -537,7 +537,8 @@ void iwl_mld_mac80211_stop(struct ieee80211_hw *hw, bool suspend)
 	/* if the suspend flow fails the fw is in error. Stop it here, and it
 	 * will be started upon wakeup
 	 */
-	if (!suspend || iwl_mld_no_wowlan_suspend(mld))
+	if (!suspend ||
+	    (IS_ENABLED(CONFIG_PM_SLEEP) && iwl_mld_no_wowlan_suspend(mld)))
 		iwl_mld_stop_fw(mld);
 
 	/* HW is stopped, no more coming RX. OTOH, the worker can't run as the
@@ -1943,6 +1944,7 @@ static void iwl_mld_sta_rc_update(struct ieee80211_hw *hw,
 	}
 }
 
+#ifdef CONFIG_PM_SLEEP
 static void iwl_mld_set_wakeup(struct ieee80211_hw *hw, bool enabled)
 {
 	struct iwl_mld *mld = IWL_MAC80211_GET_MLD(hw);
@@ -1994,6 +1996,7 @@ static int iwl_mld_resume(struct ieee80211_hw *hw)
 
 	return 0;
 }
+#endif
 
 static int iwl_mld_alloc_ptk_pn(struct iwl_mld *mld,
 				struct iwl_mld_sta *mld_sta,