Share magic word of HRR

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 f5d791f..4332a1d 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -34,6 +34,12 @@
 #include "ssl_tls13_keys.h"
 #include "ssl_debug_helpers.h"
 
+const uint8_t mbedtls_ssl_tls13_hello_retry_request_magic[32] =
+               { 0xCF, 0x21, 0xAD, 0x74, 0xE5, 0x9A, 0x61, 0x11, 0xBE,
+                 0x1D, 0x8C, 0x02, 0x1E, 0x65, 0xB8, 0x91, 0xC2, 0xA2,
+                 0x11, 0x16, 0x7A, 0xBB, 0x8C, 0x5E, 0x07, 0x9E, 0x09,
+                 0xE2, 0xC8, 0xA8, 0x33 ,0x9C };
+
 int mbedtls_ssl_tls13_fetch_handshake_msg( mbedtls_ssl_context *ssl,
                                            unsigned hs_type,
                                            unsigned char **buf,