wifi-scripts: ucode: fix EAP phase2 authentication method

The supplicant config generator emitted the phase2 directive as
phase2="auth=${auth}" for every PEAP/TTLS/FAST configuration. That is
wrong whenever the configured inner method is an EAP method: for
auth='EAP-MSCHAPV2' it produced phase2="auth=EAP-MSCHAPV2", which
wpa_supplicant rejects with:

  TLS: Unsupported Phase2 EAP method 'EAP-MSCHAPV2'

breaking WPA-Enterprise clients that use an EAP inner method.

Mirror the shell config generator (hostapd.sh): strip the "EAP-" prefix
and pick the phase2 prefix from the method type, i.e. "autheap=" for a
tunneled EAP method with TTLS and "auth=" for a non-EAP method or a
full "auth=..." spec provided by the user.

Fixes: https://github.com/openwrt/openwrt/issues/24086
Fixes: c92ded2f6e ("wifi-scripts: fix EAP STA support in supplicant config generation")
Assisted-by: Claude:claude-opus-4-8
Link: https://github.com/openwrt/openwrt/pull/24088
(cherry picked from commit 0cdf956ee1)
Link: https://github.com/openwrt/openwrt/pull/24116
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/network/config/wifi-scripts/files-ucode/usr/share/ucode/wifi/supplicant.uc

@@ -160,7 +160,20 @@ function setup_sta(data, config) {
 		case 'peap':
 		case 'ttls':
 			set_default(config, 'auth', 'MSCHAPV2');
-			config.phase2 = `"auth=${config.auth}"`;
+
+			let auth = config.auth;
+			let phase2proto = 'auth=';
+			if (index(auth, 'auth') == 0) {
+				/* user already provided a full "auth=..." spec */
+				phase2proto = '';
+			} else if (index(auth, 'EAP-') == 0) {
+				/* inner EAP method, e.g. EAP-MSCHAPV2 -> MSCHAPV2 */
+				auth = substr(auth, 4);
+				if (config.eap_type == 'ttls')
+					phase2proto = 'autheap=';
+			}
+			config.phase2 = `"${phase2proto}${auth}"`;
+
 			if (config.auth == 'EAP-TLS') {
 				if (config.ca_cert2_usesystem && fs.stat('/etc/ssl/certs/ca-certificates.crt'))
 					config.ca_cert2 = '/etc/ssl/certs/ca-certificates.crt';