Don't use const var in initialization of another const var

ARM Compiler doesn't like it.
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 4afb27c..559c881 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -3389,11 +3389,10 @@
             mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
             == MBEDTLS_KEY_EXCHANGE_ECDHE_RSA )
         {
-            static const uint16_t secp256r1_tls_id = 23;
             static const unsigned char ecdh_param_hdr[] = {
                 MBEDTLS_ECP_TLS_NAMED_CURVE,
-                ( secp256r1_tls_id >> 8 ) & 0xFF,
-                ( secp256r1_tls_id >> 0 ) & 0xFF,
+                0  /* high bits of secp256r1 TLS ID  */,
+                23 /* low bits of secp256r1 TLS ID   */,
                 2 * NUM_ECC_BYTES + 1,
                 0x04 /* Uncompressed */
             };