net: sh_eth: change the condition of initialization

The SH7757 has 2 Fast Ethernet and 2 Gigabit Ethernet, and the first
Gigabit channel needs the initialization. So, this patch adds the
parameter of "needs_init", and if the sh_eth_plat_data is set it
to 1, the driver will initialize the channel.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>