sh_eth: remove EDMAC_BIG_ENDIAN

Commit  71557a37 ("[netdrvr] sh_eth: Add SH7619 support") added support
for the big-endian EDMAC descriptors. However, it was never used and never
worked right until the recent driver  fixes. I think we now  can just remove
this support,  it was only burdening the driver from the start. It should be
easy to do without disturbing the SH platform code, at least for now...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>