Unify parsing of the signature algorithms extension

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 46a6a49..ce8c402 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -651,7 +651,7 @@
             case MBEDTLS_TLS_EXT_SIG_ALG:
                 MBEDTLS_SSL_DEBUG_MSG( 3, ( "found signature_algorithms extension" ) );
 
-                ret = mbedtls_ssl_tls13_parse_sig_alg_ext(
+                ret = mbedtls_ssl_parse_sig_alg_ext(
                           ssl, p, extension_data_end );
                 if( ret != 0 )
                 {