eth: Add 10G Ethernet MAC module and testbench

Signed-off-by: Alex Forencich <alex@alexforencich.com>

rtl/eth/taxi_eth_mac_10g.f

@@ -0,0 +1,10 @@
+taxi_eth_mac_10g.sv
+taxi_axis_xgmii_rx_64.sv
+taxi_axis_xgmii_tx_64.sv
+taxi_axis_xgmii_rx_32.sv
+taxi_axis_xgmii_tx_32.sv
+taxi_mac_ctrl_tx.sv
+taxi_mac_ctrl_rx.sv
+taxi_mac_pause_ctrl_tx.sv
+taxi_mac_pause_ctrl_rx.sv
+../lfsr/taxi_lfsr.sv