ARM: dts: r7s72100: Add support for GR-Peach

Add device tree source for Renesas GR-Peach board.
GR-Peach is an RZ/A1H based board with 10MB of on-chip SRAM and 8MB
QSPI flash storage.
Add support for the board, and create a 2MB partition to use as rootfs.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>