Rename write signature algorithms function

To keep similar name with other place.

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index 4b087ba..1713d4c 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -73,7 +73,7 @@
 #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
 
 /*
- * mbedtls_ssl_tls13_write_signature_algorithms_ext( )
+ * mbedtls_ssl_tls13_write_sig_alg_ext( )
  *
  * enum {
  *    ....
@@ -90,11 +90,10 @@
  * Only if we handle at least one key exchange that needs signatures.
  */
 
-int mbedtls_ssl_tls13_write_signature_algorithms_ext( 
-    mbedtls_ssl_context *ssl,
-    unsigned char *buf,
-    unsigned char *end,
-    size_t *olen )
+int mbedtls_ssl_tls13_write_sig_alg_ext( mbedtls_ssl_context *ssl,
+                                         unsigned char *buf,
+                                         unsigned char *end,
+                                         size_t *olen )
 {
     ((void) ssl);
     ((void) buf);