sh_eth: sh_eth_close() always returns 0

sh_eth_close() always returns 0, hence the check in sh_eth_wol_restore()
is pointless (however we cannot change the prototype of sh_eth_close() as
it implements the driver's ndo_stop() method).

Found by Linux Verification Center (linuxtesting.org) with the SVACE static
analysis tool.

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>