dt-bindings: arm: Add Google Coral Edge TPU entry

Add Google Coral Edge TPU, named as imx8mq-phanbell, to the
imx8mq supported devices.

Signed-off-by: Marco Franchi <marco.franchi@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>