arm64: dts: zii-ultra: Add node for accelerometer

Add I2C node for accelerometer present on both Zest and RMB3 boards.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Shawn Guo <shawnguo@kernel.org>