Documentation: DT: Add entry for FSL LS1012A RDB, FRDM, QDS boards

Signed-off-by: Harninder Rai <harninder.rai@nxp.com>
Signed-off-by: Bhaskar Upadhaya <Bhaskar.Upadhaya@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>