ARM: dts: r7s9210-rza2mevb: Add support for RZ/A2M EVB

Add support for Renesas RZ/A2M evaluation board.

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>