net: sh_eth: Add support SH7734

Add define of SH7734 register and sh_eth_reset_hw_crc function.

V3: Rebase net/HEAD.
V2: Do not split line of #if defined.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>