Add c_eth_tester_bg_block_len_max.

libraries/io/eth/src/vhdl/eth_tester_pkg.vhd

@@ -33,6 +33,8 @@ USE common_lib.common_network_layers_pkg.ALL;
 
 PACKAGE eth_tester_pkg is
 
+  CONSTANT c_eth_tester_bg_block_len_max  : NATURAL := c_network_eth_payload_jumbo_max;  -- 9000 octets
+
   -- hdr_field_sel bit selects where the hdr_field value is set:
   -- . 0 = data path controlled, value is set in data path, so field_default() is not used.
   -- . 1 = MM controlled, value is set via MM or by the field_default(), so any data path setting in