sh_eth: kill unneeded typecast in sh_eth_drv_probe()

sh_eth_drv_probe() does cast from 'void *' when assigning to the 'pd'  variable
which is automatic anyway. Turn the assignment into initializer, while removing
the cast...

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