dt-bindings: arm: fsl: Add MSC SM2S-IMX8PLUS SoM and SM2-MB-EP1 Carrier

Add DT compatible strings for a combination of the 14N0600E variant of
the Avnet (MSC branded) SM2S-IMX8PLUS SoM on it's own and in combination
with the SM2-MB-EP1 carrier board.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>