wifi: wireless: avoid strlen() in cfg80211_michael_mic_failure()

In 'cfg80211_michael_mic_failure()', avoid extra call to 'strlen()'
by using the value returned by 'sprintf()'. Compile tested only.
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Link: https://msgid.link/20240110054246.371651-1-dmantipov@yandex.ruSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/mlme.c

@@ -241,12 +241,12 @@ void cfg80211_michael_mic_failure(struct net_device *dev, const u8 *addr,
 	char *buf = kmalloc(128, gfp);
 
 	if (buf) {
-		sprintf(buf, "MLME-MICHAELMICFAILURE.indication("
-			"keyid=%d %scast addr=%pM)", key_id,
-			key_type == NL80211_KEYTYPE_GROUP ? "broad" : "uni",
-			addr);
 		memset(&wrqu, 0, sizeof(wrqu));
-		wrqu.data.length = strlen(buf);
+		wrqu.data.length =
+			sprintf(buf, "MLME-MICHAELMICFAILURE."
+				"indication(keyid=%d %scast addr=%pM)",
+				key_id, key_type == NL80211_KEYTYPE_GROUP
+				? "broad" : "uni", addr);
 		wireless_send_event(dev, IWEVCUSTOM, &wrqu, buf);
 		kfree(buf);
 	}