arm64: defconfig: Enable configs for Toshiba Visconti

Enable support for the Toshiba Visconti SoCs.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Reviewed-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>