Add const to move variables to .rodata section

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index af65e6d..1e1d0e5 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -4348,7 +4348,7 @@
     MBEDTLS_SSL_IANA_TLS_GROUP_NONE
 };
 
-static int ssl_preset_suiteb_ciphersuites[] = {
+static const int ssl_preset_suiteb_ciphersuites[] = {
     MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
     MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
     0