sh_eth: get SH7757 support out of #ifdef

Get the SH7757 code/data in the driver out of #ifdef by adding "sh7757-ether"
and "sh7757-gether" to the platform driver's ID table.  Note that we can remove
SH_ETH_HAS_BOTH_MODULES and sh_eth_get_cpu_data().
Change the Ether/GEther platform devices' names in the SH platform code
accordingly.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>