net: sh_eth: add the value of tsu to the SH7757's GETHER

The SH7757's GETHER has TSU registers. So, this patch adds the value
of ".tsu = 1" in the sh_eth_cpu_data.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>