sh: Add support SH7710/SH7712

SH7710/SH7712 of SH3 CPU are supported.
SH771X is called SH-Ether, and has the Ether controller in CPU.
The driver of Ether is not included in this patch.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>