arm64: dts: imx8qxp: add lsio_mu2 node

Add lsio_mu2 node which could be used communicate with SCU.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>