ARM: dts: r8a7742-iwg21d-q7: Add SPI NOR support

Add support for the SPI NOR device which is connected to MSIOF0 interface
on the iWave RainboW-G21d-q7 board.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Link: https://lore.kernel.org/r/20200907155541.2011-2-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>