sh_eth: reuse sh_eth_chip_reset()

All the chip_reset() methods repeat the code writing to the ARSTR register
and delaying for 1 ms, so that we can reuse sh_eth_chip_reset() twice.

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