arm64: dts: imx8qxp: add alias for lsio MU

Add lsio mu alias for all lsio MUs that could communicate with SCU,
imx_scu_enable_general_irq_channel will parse the alias to get
the mu resource id, if using other MU, not MU1, the `mu_resource_id`
is not what we expect, so add alias to fix this issue.

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