dt-bindings: arm: toshiba: Add the TMPV7708 VisROBO VRB board

Add an entry for the Toshiba Visconti TMPV7708 VisROBO VRB board
(tmpv7708-visrobo-vrb) to the board/SoC bindings.

Signed-off-by: Yuji Ishikawa <yuji2.ishikawa@toshiba.co.jp>
Link: https://lore.kernel.org/r/20211014092703.15251-3-yuji2.ishikawa@toshiba.co.jp


Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>