sh_eth: get SH771x support out of #ifdef

Get the SH771[02] data in the driver out of #ifdef by adding "sh771x-ether" to
the platform driver's ID table. Change the Ether platform device's name in the
SH platform code accordingly.

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