WPS: Fix wps_reg nfc-pw option

Commit ffdaa05a6b1b59c4b2e50f9b7fef82769fc2d3fe added support for using
NFC password token from an AP. However, it had a bug that prevented the
wpa_supplicant wps_reg command from being used with "nfc-pw" as the PIN
value. Fix string comparison to handle this correctly.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>

src/eap_peer/eap_wsc.c

@@ -194,7 +194,8 @@ static void * eap_wsc_init(struct eap_sm *sm)
 			cfg.pin = dev_pw;
 			cfg.pin_len /= 2;
 		}
-		if (cfg.pin_len == 6 && os_strncmp(pos, "nfc-pw", 6) == 0) {
+		if (cfg.pin_len == 6 &&
+		    os_strncmp((const char *) cfg.pin, "nfc-pw", 6) == 0) {
 			cfg.pin = NULL;
 			cfg.pin_len = 0;
 			nfc = 1;