arm64: dts: fsl-ls1028a-qds: Drop overlay syntax hard coding

As suggested by commit 9ae8578b ("of: Documentation: change overlay
example to use current syntax"), there is no need to have overlay syntax
be hard coded in the device tree source file any more.

Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>