sh_eth: fix descriptor access endianness

The driver never  calls cpu_to_edmac() when writing the descriptor address
and edmac_to_cpu() when reading it, although it should -- fix this.

Note that the frame/buffer length descriptor field accesses also need fixing
but since they are both 16-bit we can't  use {cpu|edmac}_to_{edmac|cpu}()...

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