sh_eth: fix typo in EESR.TRO bit name

The  correct name of the EESR bit 8 is TRO (transmit retry over), not RTO.
Note that EESIPR bit 8, TROIP remained correct...

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