dt-bindings: arm: fsl: update TQ-Systems SoMs and boards based on i.MX7

Introduce compatible strings for the TQMa7x SoMs.

Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>