dt-bindings: arm: fsl: add TQ-Systems LS1021A board

TQMLS102xA is a SOM family using NXP LS1021A CPU family.
MBLS102xA is an evaluation mainboard for this SOM.

Signed-off-by: Matthias Schiffer <matthias.schiffer@tq-group.com>
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>