sh_eth: get register layout from 'struct sh_eth_cpu_data'

The register layout is a SoC characteristic, so it's wrong that it's stored
in the otherwise board specific platform data. Add 'register_type' field to
'struct sh_eth_cpu_data', initialize it properly for each SoC, and read  it
from this structure instead of the platfrom data from now on...

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