net: sh_eth: Add support SH7734 Ethernet device

SH7734 has one channel ethernet device.
This support 10/100/1000Base, and RMII/MII/GMII.
And this has the same structure as SH7763.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>