wl1251: check return from call to wl1251_acx_arp_ip_filter

Currently the less than zero error check on ret is incorrect
as it is checking a far earlier ret assignment rather than the
return from the call to wl1251_acx_arp_ip_filter. Fix this by
adding in the missing assginment.

Detected by CoverityScan, CID#1164835 ("Logically dead code")

Fixes: 204cc5c44fb6 ("wl1251: implement hardware ARP filtering")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ti/wl1251/main.c

@@ -1200,8 +1200,7 @@ static void wl1251_op_bss_info_changed(struct ieee80211_hw *hw,
 		WARN_ON(wl->bss_type != BSS_TYPE_STA_BSS);
 
 		enable = bss_conf->arp_addr_cnt == 1 && bss_conf->assoc;
-		wl1251_acx_arp_ip_filter(wl, enable, addr);
-
+		ret = wl1251_acx_arp_ip_filter(wl, enable, addr);
 		if (ret < 0)
 			goto out_sleep;
 	}