[U-Boot] 83xx, uec: adjust enet_interface settings on the fly.

[Liu Dave-R63238]

> > I don't remember why I added the eth_type==GIGA_ETH condition.
> > If it is possible, please refactor it as Kim.
> 
> Hmm.. while looking at this code, a question comes in mind:
> Did this code (eth_type==GIGA_ETH) work correctly?

Yes, It worked correctly. But later there are lots of change,
I'm not sure if it is correct right now. 

> I see there is a switching possible from 1000 to 100 or 10, 
> but never back to 1000, because the 1000 case did nothing ...?
> Is this intentionally?

The code was assuming the initial speed is 1000Mbps, so
the 1000 case did nothing. 

> Also uec->uec_info->enet_interface is never updated, which 
> should be done ... or?

IIRC, the enet_interface was designed for interface type according
to board design. So it was placed on uec_info, it is never updated.
eg: SGMII if board is SGMII connection
      RGMII if board is RGMII connection...
      RMII if board is RMII....

Thanks, Dave