wilc1000: fix compiler warning for 'wowlan_support' unused variable

Avoid below reported warning found when 'CONFIG_PM' config is
undefined.

'warning: unused variable 'wowlan_support' [-Wunused-const-variable]'
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200710051826.3267-4-ajay.kathat@microchip.com

drivers/net/wireless/microchip/wilc1000/cfg80211.c

@@ -46,9 +46,11 @@ static const struct ieee80211_txrx_stypes
 	}
 };
 
+#ifdef CONFIG_PM
 static const struct wiphy_wowlan_support wowlan_support = {
 	.flags = WIPHY_WOWLAN_ANY
 };
+#endif
 
 struct wilc_p2p_mgmt_data {
 	int size;