modify according to the change of keystore interface.

Change-Id: I1fe2ee40ac60ed858322a1ab38e6aec63820eda1
diff --git a/wpa_supplicant/src/crypto/tls_openssl.c b/wpa_supplicant/src/crypto/tls_openssl.c
index 849358f..3d468ec 100644
--- a/wpa_supplicant/src/crypto/tls_openssl.c
+++ b/wpa_supplicant/src/crypto/tls_openssl.c
@@ -55,7 +55,7 @@
 {
 	BIO *bio = NULL;
 	char value[KEYSTORE_MESSAGE_SIZE];
-	int length = keystore_get(key, value);
+	int length = keystore_get(key, strlen(key), value);
 	if (length != -1 && (bio = BIO_new(BIO_s_mem())) != NULL) {
 		BIO_write(bio, value, length);
 	}